Japanese Aircraft In Royal Thai Air Force and Royal Thai Navy Service During WWII
by Jan Forsgren [janforsgren (at) yahoo.se]
During World War II , Thailand was a reluctant ally to Japan . During the 1930's, the USA had been the main supplier of aircraft to Siam , as Thailand was then known. During the Franco-Thai war in 1940-1941, Thailand had received support from Japan , including aircraft. After Japan had attacked Thailand on December 8, 1941 , a Pact of Alliance between Japan and Thailand was signed on December 21, 1941 . The old Thai proverb, that the tree that bends with the wind is the tree that survives the storm, was indicative of the Thai mentality. Nearly hundred Japanese aircraft of eight different types were delivered to the Royal Thai Air Force between 1940 and 1943. Nine former Netherlands East Indies Air Force, NEIAF, Martin bombers were supplied to the RTAF by Japan as well. The Royal Thai Navy received 27 Japanese aircraft of three different types between 1938 and 1944. Contacts between Japan and Siam , as Thailand was known until 1939, had been tentative. Siam had until the late ‘twenties relied heavily on France as the main supplier of military aircraft. By the early 1930s however, the American companies Curtiss and Vought had taken over after the French, delivering Hawk II and III fighters and V.93S Corsair light attack aircraft to the Siamese Royal Aeronautical Service, while the British designed Avro 504N served as primary trainers. Both Curtiss Hawk III's and Corsairs were produced under licence in Siam , as was the Avro 504N.
A non-stop flight between Tokyo and Bangkok had taken place in 1936, along with several proving flights during October and November the same year. During 1936, negotiations between Dai Nippon Koku Kaishu (Greater Japan Air Lines) led to an agreement, signed on November 1, 1936 , of opening a regular airline service between Tokyo and Bangkok , beginning February 1, 1940 . The route would stretch from Fukuota – Taihotu ( Taipei ) – Hanoi and Bangkok . Lengthy negotiations with the French authorities in Hanoi meant that the first regular service was flown during June, 1940 instead of February.
The Royal Aeronautical Service was originally organized as part of the Army, not becoming a separate and independent branch of the Siamese armed forces until April 12, 1937 . The new service was known as the Royal Siamese Air Force, being re-named yet again in 1939 as the Royal Thai Air Force. By the late 1930's, the Royal Siamese Navy had plans for an air arm as well. Although the Navy had had little interest in aviation matters, their attitude changed after the 1932 coup d'etat. In 1935, two 1,400 ton corvettes, named the Tachin and the Maeklong, were ordered from Japan . A small observation floatplane was to be operated from each corvette. Apart from pilot training, there seems to have been very little contact or co-operation between the Royal Siamese Air Force and the Royal Siamese Navy. In 1937, several Naval officers were sent to the Air Force flying school at Don Muang. Although coastal reconnaissance was the responsibility of the Royal Siamese Navy, no aircraft had been acquired. Three sets of metal floats, manufactured by Edo , were purchased by the Royal Aeronautical Service for use on its Corsairs. No Corsairs were ever equipped with floats, though.
As the plans of acquiring observation aircraft went ahead, the Royal Siamese Navy entered negotiations with the Watanabe Tekkosho K.K. (Watanabe Iron Works, Ltd.) regarding the supply of such an aircraft. The Watanabe company had designed a small observation biplane, known as the Watanabe E9W1, that would be able to operate from large u-boats. The Royal Siamese Navy observation aircraft was based on the E9W1, but with a slightly bigger span and length. Although similar in appearance, the WS-103S and the E9W1 were two different types of aircraft. The WS-103S was designed and built specifically for the Royal Siamese Navy. Two naval officers had been dispatched to Japan in November 1937, to oversee the construction of the new aircraft. The first flight occured during February 1938, with the six aircraft ordered being delivered in May 1938. The Siamese variant was designated the WS-103S (the S standing for Siam ), of which six were delivered to the Royal Siamese Navy in May 1938. In the Watanabe WS-103S, the Royal Siamese Navy had an aircraft able to perform its intended duties of observation and scouting, being equipped with a short-wave radio. Its arnament consisted of three Madsen 8-mm machine guns, one in the fuselage and two mounted in the upper wing. One additional machine gun was operated by the observer. As an extra set of flight controls could be installed in the rear cockpit, the WS-103S could also be used as an advanced trainer. Incidentally, small numbers of theWatanabe E9W1 were ordered by the Imperial Japanese Navy. A few were still in service during the early months of the Pacific War, earning the Allied codename “Slim.” According to a 1938 report in the Swiss aviation magazine “Interavia”, 200 Siamese officers were to receive training by the Imperial Japanese Air Force. Although negotiations were being conducted with both the USA and Great Britain , the Japanese influence on aviation in Siam appeared to be on the increase, with the delivery of the WS-103S's, as well as negotiations on airfield construction.
During the Franco-Thai war in 1940-1941, Japan had supported Thailand , supplying bomber aircraft. A series of incidents between French colonial forces in Indochina and Thailand escalated into open war in late November, 1940. The war ended on January 28, 1941 , after Japanese diplomatic intervention. France was forced to cede a considerable amount of territory to Thailand . The Royal Thai Air Force had acquitted itself well, claiming five French aircraft as shot down, with another 17 destroyed in bomb raids. The RTAF had suffered losses as well, admitting losing three aircraft as shot down, and between five and ten destroyed on the ground in air raids. Yet another three aircraft were lost in accidents. One Corsair was captured by French forces. Thirteen air crew had been killed and another five wounded. During the evening of December 7, 1941 , the Thai Government received a request from Japan to allow Japanese troops to pass Thai territory for attacking British forces in Burma and Malaya . If this request was used, Japan would use force. While the issue was being debated, the Japanese attacked. The first Japanese forces crossed the border around 0400 hours the next day, December 8. The Japanese invasion force landed at four different places along the Thai coastal provinces, including Samut Prakarn south of Bangkok . The Thai forces resisted as best they could, but were overwhelmed by the numerically superior Japanese forces. Three Hawk III's were shot down during take off from Weatatna Nakorn airfield at Aranya Prathet by 11 Nakajima Ki-27bs of the 77 th Sentai, while at Prachaub Kirikhan, at least two Hawk III's were lost by the resident 7 th Wing. On 0730, a cease-fire was reached. The RTAF had by then lost 39 men, mostly at Prachaub Kirikhan, and at least five aircraft, including five Curtiss Hawk III's. In return, about 400 Japanese soldiers had been killed or wounded by the Thai defenders.
A Pact of Alliance between Japan and Thailand was signed on December 21, 1941 . One week earlier, on December 14, the Thai Prime Minister Phibun had agreed to a Japanese request of supporting Japanese forces on the northern Burmese front. This would include both Army and Air Force units. The RTAF was reluctant to co-operate with the Japanese, but there didn't seem to be any alternative. Air Vice-Marshal Athuk stated that the RTAF had no choice but to carry out Prime Minister Phibuns orders and act as professionals. Traditionally, the RTAF had had strong ties with France , Great Britain and the USA , but there was no option other than becoming a reluctant ally to Japan . The Kong Bin Yai Phasom Phak Payab (Northern Combined Air Wing) was formed, being based at Lampang. Three squadrons, Foong Bin 21, equipped with nine Corsairs, Foong Bin 41, equipped with ten Curtiss Hawk III's and Foong Bin 62 with nine Ki-21-Ibs. When the pacific war started, the RTAF changed its insignia from a roundel in the Thai colours, blue, white and red, to a rectangle in the same colours as the Thai flag. During late 1942, the RTAF national markings were changed yet again to a red rectangle upon which a white elephant was superimposed. The change of the national insignia was made to avoid confusion with French and British aircraft.
Royal Thai Air Force
The fighter squadrons of the RTAF operated Curtiss Hawk III's and Hawk 75Ns. Their intended replacement was the North American N.A.-68, six of which had been ordered in late 1939. It was intended to produce sufficient numbers of N.A.-68s under licence to replace all Hawk III's and Hawk 75Ns. But, due to a US embargo in October 1940, no N.A.-68s were delivered to Thailand . New fighter aircraft, 12 Nakajima Ki-27bs, arrived in early 1942. Prior to the delivery of the fighters, Japan provided training and technical assistance to the RTAF. The Ki-27bs were ordered from the Mansyu company in late January 1942. The Ki-27b was in large scale service with the Imperial Japanese Army Air Force, IJAAF, being known to the Allies as “Nate.” The Thais named some of the Japanese aircraft types after the the city where they had been manufactured. Thereby, the Ki-27bs were known as Otas, after the city of Ota . They also received the designation B.Kh12, Fighter type 12, as well as being known in the separate classification system as the Type 15. They were painted in the standard IJAAF colours of dark green upper sides and light green undersides. However, some Ki-27bs were painted in a two tone dark green and brown upper sides during the war.
Upon delivery, the Otas were allocated to the Foong Bin 16, supplementing Hawk 75Ns. From February 6, 1942 , when the first mission was flown, the Ki-27bs flew escort for the Ki-21s and Ki-30 bombers during bombing and reconnaissance missions over the Shan states, as well as maintaining combat air patrols over northern Thailand . In late 1943, Foong Bin 16 was based at Lampang in northern Thailand . During the closing months of 1943, Consolidated B-24s of the Chinese based 308 th BG on three occasions raided Chiang Mai and Lampang. During the third raid, on December 31, six Ki-27bs tried to intercept the US bombers. No actual attacks on the B-24s by the Thai fighters seem to have been carried out. The US crews later reported that the fighters veered off and did not return return fire. During 1944, more and more raids were flown against targets in Thailand . On November 11, 1944 , nine P-51 Mustangs from the 25 th FS and eight P-38 Lightnings flew an offensive reconnaissance mission over northern Thailand . Their targets included the railway line between Chiang Mai and the Ban Dara bridge, as well as the airfields in the area. A locomotive was attacked, and damaged, and the American fighters also attacked Lampang airfield, destroying a single-engined aircraft on the runway.
The Thai defences had been alerted to the raid, and scrambled five Ki-27bs from Foong Bin 16. After the Lightnings and Mustangs had completed their strafing run, the RTAF fighters were bounced by the US pilots. Although the Otas were more nimble than the P-38s and P-51s, they could not match the speed and arnament of the US fighters. During the rather one-sided melee, the Thais claimed one P-38 as shot down, but in turn lost all of their Ki-27bs. The five RTAF fighters split into two sections, with Pilot Officer Kamrop Bleangkam and Chief Warrant Officer Chuladit Detkanchorn attacking the Lightnings. P/O Kamrop claimed one P-38 before his own aircraft was badly hit, and he was forced to crash land. The P-38s shot down Chief W/O Chuladit as well. As the other three Thai pilots tried to fend off the P-51s, all of them were shot down. Flight Lieutenant Chalermkiats Ota was hit in the engine. He made a forced landing, after which his Ki-27b was strafed and destroyed by one of the Mustangs. Of the other two Thai pilots, Chief W/O Nat Thara Kaimuk crashed nine miles from Lampang, while Chief W/O Nat Sunthorn was the only Thai pilot killed. All the other Thai pilots were injured, though. The USAAF lost one aircraft, most probably the P-38 claimed by P/O Kamrop. According to Thai sources, three Mustangs were damaged during the dogfight, two of which crashed in northern Thailand and the last in the Shan states.
As eight Ki-27bs (of which two were serviceable) are listed in the RTAF Order of Battle for April, 1945, it is possible that the RTAF received a few Ki-27bs as attrition replacements. By November 1945, only one Ota was serviceable.
Incidentally, the Ki-27b wreck at the RTAF Museum has no connection to the Royal Thai Air Force. The wreck is a former IJAAF Ki-27, and was discovered by local fishermen near Nakhon Si Thammarat in January 1981.
During 1943, the first of 24 Nakajima Ki-43II b Hayabusa fighters were delivered, the first of which were handed over in Singapore . The Ki-43 was the Imperial Japanese Army Air Force most numerous fighter, being known under the Allied code name “Oscar.” The Ki-43s, although already outclassed by Allied fighters, represented a great increase in performance (as compared to the old Curtiss Hawks and even the Ki-27bs). In RTAF service, the Hayabusas were designated B.Kh13, Fighter type 13, and in the paralel classification system as Type 14. The RTAF pilots usually referred to the Ki-43 with its Japanese name, Hayabusa (Peregrine Falcon). Most Hayabusas went to a specially formed fighter squadron, Foong Bin 15, being based at Don Muang. During the summer of 1944, the RTAF asked for more Hayabusas, to equip a further two or three squadrons. As the Japanese forces were on the retreat on every front, few aircraft of any type could be spared. However, three more Ki-43s were delivered as attrition replacements. Several intercept missions were flown by the RTAF Hayabusas. The first of these occured on June 5, 1944 , when, during a raid on Bangkok , three Ki-43s made an unsuccessful attempt at intercepting 55 USAAF B-29s. On November 18, 1944 , ten USAAF B-24s attacked Bangkok , and of the three Ki-43s sent to intercept the raiders, FS 1 st Class Wichien Buranalekha managed to inflict damage to one of the B-24s. The biggest raid on Bangkok during the war occured on November 2, 1944 , when the marshalling yards at Bang Sue were raided by 55 B-29s. Seven Hayabusas from Foong Bin 16, along with 14 Ki-43s of the Imperial Japanese Army Air Force, IJAAF, attempted to intercept the huge B-29s. One of the Hayabusa pilots, Flt Lt Therdsak Worrasap, attacked a B-29, damaging it. However, Therdsak was shot down by return fire. He managed to bail out of his stricken Hayabusa over Petchburi, having received severe burns. The B-29 crews reported 45 attacks, with seven enemy fighters shot down. One of the B-29s was lost, possibly the one damaged by Flt Lt Therdsak. Flt Lt Therdsak, as well as Pilot Officer Kamrop, were later awarded with their second Medal of Valour. Both pilots had received their second Medal of Valour during the Franco-Thai air war. On January 3, 1945 , 44 USAAF B-29s attacked the Rama VI bridge in Bangkok . The RTAF sent a number of Ki-43s, and, amazingly, Hawk III's to intercept the raid. The RTAF fighters were unable to reach the B-29s, however.
The RAF and USAAF bomb raids put the RTAF in an awkward position. As the Air Force was engaged in transporting Allied secret agents to Don Muang, it also had to counter the Allied air raids. To suppress Japanese suspicions, the RTAF continued to try to intercept Allied bombers. As the Allied air supremacy grew even more, most airfields in Thailand were attacked by USAAF fighter-bombers. Even though the RTAF was secretly supporting the Allied cause, the Allied pilots had no way of distinguishing RTAF aircraft from Japanese operated aircraft. In one such raid, on April 7, 1945 , Don Muang was attacked by USAAF P-51 Mustangs. In this attack alone, the RTAF lost seven aircraft destroyed and seven personnel killed. During another raid on Don Muang two days later, two RTAF Ki-43s attempted to intercept about 40 USAAF P-51 Mustangs. Both Ki-43s were damaged, and the Thai pilots had to force land their Hayabusas. The strafing attack cost the RTAF yet another four aircraft, including one Ki-30. Several IJAAF aircraft were claimed as destroyed or damaged as well.
In April 1945, 14 Ki-43s (of which four were serviceable) were still in service. By November, only three Hayabusas were operational. Presumably, further Ki-43s were made airworthy by cannibalisation after the end of the war. Post war, the Ki-43s were stripped off their camouflage, and the pre-war RTAF roundel reinstated. The Nakajima Ki-43s saw action one last time in 1948, when rebels around the Song Khla province in southern Thailand attacked government forces. The rebels were inspired by the Malayan communist rebel Chin Peng. In response to the insurgency, the Thai Government sent Army and Air Force units to the south. The last Ki-43s were finally retired in 1949. The Hayabusas were initally painted in the standard IJAAF camouflage, dark green upper sides and light grey undersides. Some aircraft were painted in a “tiger stripe” camouflage, consisting of light brown and green with natural metal undersides.
Reports that the RTAF operated a number of Mitsubishi A6M2 and A6M5 Zeros are without foundation. Most likely, the reported Zeros were the few Nakajima Ki-43 Hayabusas that remained in service with the RTAF after the end of the war.
GLIDERS, TRAINERS AND OBSERVATION AIRCRAFT
In 1941, three Japanese gliders were supplied to the RTAF. These three gliders, all built by the Nihon Kogata company, consisted of one Tobi primary glider, one Hato elementary glider and one Ootori soarer. Amazingly, both the Tobi and the Hato gliders survived the ravages of World War II, and have been preserved by the RTAF Museum at Don Muang.
At the same time as the Ki-27bs were ordered, January 1942, the RTAF also ordered 24 Tachikawa Ki-36 and Ki-55 “Ida” aircraft. The Ki-36 was a two-seat light ground support aircraft, while the similar Ki-55s were advanced trainers. It is unknown whether the Ki-36s were employed operationally, or just used as advanced trainers. The Ki-36 had been widely used on operations in China by the Imperial Japanese Army Air Force, but it may have been considered to be of limited operational use by the RTAF, except as an advanced trainer. The exact quantity of Ki-36s and Ki-55s respectively are not known, but it could well be that only Ki-55 advanced trainers were delivered. In RTAF service, the Tachikawas were known as Bin Fuk Hat, B.F6, literally Trainer, Type 6 and in the separate classification system as the Type 89. Most of them equipped the flying school at Don Muang Air Base. To their crews, the Ki-55s were commonly known as Tachigawas.
Unfortunately, very little is known of their service in the Royal Thai Air Force is known, but in April 1945, 23 Ki-55s (of which 18 were serviceable) were listed as being in service. One was with the fighter squadron Foong Bin 15, presumably being used as a squadron hack, eight were serving with the observation squadron Foong Bin 21 and 13 equipped the training squadron Foong Bin 10. The last Ki-55 was operated by the Kong Bin Noi Phasom 80, which was attached to the Royal Thai Army. Incidentally, this Order of Battle makes no mention of any Ki-36 aircraft. By November 1945, their number had decreased to only two. In RTAF service, the Ki-55s were painted in the standard IJAAF colour scheme, dark green upper sides and light grey undersides. Post war, they were painted all yellow. One Ki-55 is preserved at the RTAF Museum .
Reportedly, the RTAF also received some Mansyu Ki-79 advanced trainers, as well as Tachikawa Ki-9 “Spruce” primary trainers. These reports are without foundation.
When, on October 10, 1940 , the US Government embargoed the N.A.-68 fighters and N.A.-69 light attack aircraft, the RTAF had to find new aircraft. A new supplier was found almost immediately, in the shape of Japan . A RTAF purchasing commission was dispatched to Japan at the end of October. Among the aircraft evaluated were the Mitsubishi Ki-21 medium bomber and the Mitsubishi Ki-30 light bomber. Both the Ki-21 and the Ki-30 were in large scale service with the Imperial Japanese Army Air Service, being known to the Allies as Sally and Ann respectively. The purchasing commission were particularly impressed by the Mitsubishi Ki-30. Consequently, an order was placed for both types, nine Ki-21s and 24 Ki-30s. Apparently, fighters of an unknown type were ordered as well, but not delivered.
The Mitsubishi Ki-30 filled the void after the N.A.-69s. The Ki-30 was easy to fly and maintain, as well as having a substantially better performance than the Corsairs. The Ki-30 was faster, its bombload was four times as high and it had twice the range compared with the Corsairs. Also, with its fixed landing gear, it could easily operate from the rough airfields in the north east. In RTAF service, the Ki-30s were known as Nagoyas, after the city of Nagoya .
All 24 Ki-30s had arrived by the end of November, having been flown to Thailand via Okinawa , Formosa , Canton , Hainan and Hanoi . Twelve of the Nagoyas were flown by Thai pilots, with Japanese pilots flying the remaining 12 aircraft. A small team of Japanese mechanics accompanied the 24 Nagoyas, being flown to Thailand in a chartered airliner from Dai Nippon Airlines. In RTAF service, the Nagoyas received the designation B.J2, Attack, type 2. In the separate classification system, it was known as Type 26.
To operate the new Ki-30s, two new squadrons, Foong Bin Phibun Songkhram 1 and 2 were formed at Don Muang. The Thai crews were able to rapidly complete their conversion training on the new Nagoyas. The first sortie was flown on January 7, 1941, when 23 Nagoyas attacked French targets in Cambodia . The following day, the nine Nagoyas, escorted by three Hawk 75Ns, attacked the airfield at Siem Reap. On January 10, the Nagoya squadrons sustained their first loss, a Ki-30 flown by Sergeant Boonyam Bansuksawat and Sergeant Boon Suksabi, was shot down by Adjuntant-Chef Tivolier, who was flying a Morane MS 406. The final air combat of the conflict took place on January 24, when nine Ki-30s and three Martin 139WS medium bombers raided Siem Reap, in an attempt to destroy the French MS 406 fighters which were based there. After the bombers had dropped their ordnance over the French airfield, a lone Nagoya , flown by Wing Commander Fuen, was attacked by two French Moranes. Wing Commander Fuens intention was to take photographs of the damage caused during the raid, but he and his gunner were set upon by two French fighters. Using all his skill, Fuen managed to avoid the attacks until the French pilots ran out of ammunition. After exhausting their ammunition the French pilots flew alongside Wing Commander Fuen, waving goodbye. Upon landing at Chantaburi, Fuen was astounded to learn that not one bullet had hit the Nagoya .
On December 22, 1941 , the two Nagoya squadrons were operated by Foong Bin 11 and 12, still being based at Don Muang. Each squadron had 11 aircraft. In January, the squadrons moved to Lampang, becoming part of the Northern Air Wing. The Ki-30s were heavily used on the Burmese front, flying bombing as well as reconnaissance missions. No Chinese fighers were encountered, but the occasional anti aircraft fire, as well as the weather and terrain, made these missions hazardous. In April 1945, 21 Ki-30s (14 serviceable) were listed as being in service. In November, 12 were still in service. The last Ki-30s were withdrawn from use in 1950. The Nagoyas were painted in the standard IJAAF colour scheme, dark green upper sides and light grey undersides.
The nine Ki-21-Ib bombers, all built under licence by Nakajima, were delivered during the end of December, 1940. In RTAF service, they received the designation Bin Thing Rabut 4, B.Th4 (Bomber type 4). In the paralel classification system, the Ki-21s were designated as the Type 61. They were not deployed during the war, because the crews had not completed their training before the end of the conflict. On April 12, 1941 , the RTAF decided to establish a heavy bomber wing, named the Kong Bin Noi 6 (the 6 th Wing). Apart from the newly delivered Ki-21s, the five remaining Martin 139Ws were part of No 6 Wing. After only a few months, the No 6 Wing was divided into two squadrons, the Foong Bin Thing Rabut 61 and 62 (The 61st and 62 nd Bomber Squadrons), of which the latter operated the Ki-21s. Both the No 61 and 62 Bomber Squadrons were based at Don Muang. By December 1, the 62 nd BS was based at Lop Buri, being a part of the Kong Bin Yai Phasom Phak Payab (Northern Combined Air Wing), with all nine Ki-21s being serviceable. The Northern Combined Air Wing was made up of Kong Bin Noi Phasom 90, with three squadrons, the Ki-21s, Foong Bin 21 equipped with nine Corsairs and Foong Bin 41 with ten Hawk III's. Initially, the Ki-21s were painted overall grey, and received camouflage later in the war, consisting of mottled green and brown over light grey.
During the Army's advance into Burma , the Ki-21s and the Martin 139Ws flew bombing missions over the Shan state. They were usually escorted by the Nakajima Ki-27bs of the Foong Bin 16. The Ki-21s were based at Koh Kha AB at lampang. As well as bombing missions, reconnaissance missions were flown along the Thai/Burmese border and over Yunnan province in China . These missions were shared with the Ki-30s, and flown by single aircraft. One Ki-21 was written off on September 6, 1942 , after having crashed into a mountain while returning from a reconaissance sortie over Kengtung. During October 1942, heavy flooding in Bangkok caused a temporary lack of food, and the Ki-21 and Martin bombers were used to deliver supplies to Don Muang.
On January 29, 1943 , Ki-21s, in concert with Ki-30s, raided the Chinese base at Mong Sae, using incendiary bombs. Several buildings, including an arms depot, was hit, and set on fire. The Chinese anti-aircraft fire hit several of the Thai bombers, although none were seriously damaged. These raids were the last of the northern campaign. A truce was arranged. Thailand had, at the behest of Japan , invaded the Shan states and fought Chinese forces. But, technically, Thailand was not at war with China . When Thailand had declared war on the Allies, China had chosen not to respond.
Despite efforts to obtain more Ki-21s and Ki-30s, no more aircraft of either type was supplied to Thailand . However, three Martin 139s and six Martin 166s were delivered in mid to late 1943. These supplemented the survivors of six Martin 139Ws (the export version of the USAAC B-10 bomber), delivered in 1937. As it turned out, these Martins were the last aircraft delivered to the Royal Thai Air Force during World War II.
On March 2, 1944 , two Curtiss P-40s of the 14 th Air Force strafed the airfield at Kengtung, destroying one or two Corsairs. The Ki-21s of the 62 nd BS, which had never been based in the Shan States, was transferred from Koh Kha AB at Lampang to Lom Sak AB in Phetchaboon province during 1943. Two Ki-21s were lost by the 62 nd BS during the war, one, as previously related on September 6, 1942 , and a second one on August 6, 1944 . The loss on August 6 occured during a transport mission over Phetchboon. On November 30, 1944 , five P-38s and four P-51s strafed the airfield at Lampang. One Ki-21, in all probability an IJAAF example, was claimed as destroyed during the attack.
Following contacts between various Thai Government officials and the Allies, several groups of agents, both from the American Office of Strategic Services (OSS) and the British Special Operations Executive (SOE) were sent to Thailand , becoming known as Force 136. It became the special task of the 61 st and 62 nd BS to pick up Allied agents, as well as supplies, and fly them to Don Muang. Rough landing strips were built in isolated parts of Thailand , including at Na An, and near Sakhon Nakhon. An airfield was also constructed at Lomsak, being able to handle the Ki-21s. During one such mission, the Martin bomber crashed, and the wreck had to be destroyed to prevent the supplies it carried from falling into Japanese hands.
In April 1945, six Ki-21s (of which four were serviceable) remained in service. By November, their number had been reduced to four. It is not known when the last Ki-21 was withdrawn from use. Parts of a Ki-21 are preserved at a railway museum in Bangkok . Whether it is the relics of a former RTAF Ki-21, or a Japanese operated example is unknown, but the remains are in very poor condition, looking like they've been through a metal mincer.
ROYAL THAI NAVY
As previously related, 27 Japanese aircraft were supplied to the Royal Thai Navy. During 1937, several Naval officers had received flight training at Don Muang. The Royal Thai navy were looking for a light twin float observation aircraft, which could also be used for training duties. The choice fell on the Watanabe WS-103S, which was dimensionally slightly larger than the Watanabe E9W1. In May 1938, six Watanabe WS.103S floatplanes, similar to the later E9W1 variant, were delivered, receiving the designation BRN.1. BRN was an abbreviation for Bor Ror Nor, meaning Royal Navy Plane in Thai. Four of the WS.103S's were based at Sattahip, equipping the 1 st Naval Squadron, while the remaining two were on Royal Thai Navy's corvettes, which, incidentally, were also built in Japan . Presumably, the Watanabes were used operationally during the Franco-Thai War. Five of the small Watanabes were still in RTN service in 1945. In RTN service, the WS-103S's were overall natural metal, with the blue, white and red Thai roundel on the wings and fuselage and the Thai flag on the fin.
Royal Thai Navy
The main operational type of the RTN was the Nakajima E8N1, 18 of which were ordered in 1938, and delivered by sea two years later, in 1940. The E8N1 was a two seat reconnaissance biplane, which also saw widespread use with the Imperial Japanese Navy, being known to the Allies under the codename “Dave”. No E8N1s were used operationally during the Franco-Thai War. Few details of their operational service are known. No information on incidents or losses have come to light, apart from the losses sustained during the Fleet Air Arm, FAA, raid on Chalong Bay, Phuket, on July 24/25, 1945. A Royal Navy task force (consisting of one aircraft carrier, HMS Ameer, one cruiser and nine destroyers) had been despatched to attack Japanese targets along the Andaman Sea . During the raid on Chalong Bay , one E8N1 was destroyed and two more damaged by FAA F6F Hellcats. Fifteen E8N1s were said to remain in active service at the end of World War II. The E8N1s were finished in the same colour scheme as the WS-103S's, although some aircraft were painted overall light grey.
The most modern aircraft supplied to the Royal Thai Navy were six Aichi E13A-1s, three in 1942 and three more in June 1944. When the first Aichi's were delivered, the 1 st naval Squadron was upgraded to a Naval Wing. The naval Wing had two bases, at Sattahip and at Chalong Bay . The Aichi E13A-1 was a three seat, twin float reconnaissance aircraft. The Aichi E13A-1 was known to the Allies as “Jake”. Their endurance made them very suitable for long patrols over the Thai coastal waters and the Gulf of Thailand , in support of Imperial Japanese Navy operations. Included among the various kinds of missions flown by the Aichi E13A-1s were naval escort, patrol and SAR. The USAAF used B-24 Liberators for bombing missions and mine laying operations along the Thai coast. Apparently, the last three E13A-1s were a gift by the Imperial Japanese Navy, IJN, as a thank you for good support during its operations. According to an unofficial source, the IJN provided the three additional E13A-1s after RTN warships and coastal units had downed at least one USAAF B-24 Liberator. Again, little is known about the Royal Thai Navy use of its Aichis. One of them was destroyed at Chalong Bay on July 24/25, 1945. Five were still in service at the end of the war. In RTN service, the Aichi E13A-1's were painted in the standard IJN colours, dark green upper sides and light grey undersides, with black cowling and a yellow identification stripe. A white, or possibly yellow, roundel with a black (or dark blue) anchor were painted on the upper and lower surfaces of the wings and on the fuselage. A Thai national flag was also painted on the fin. Shortly after the end of the War, all the remaining Japanese aircraft in RTN service were decommissioned and withdrawn from use. This was due to an informal agreement with the Allies. The Royal Thai Navy continued to operate some light aircraft, but new combat aircraft in the shape of Fairey Firefly Mk I's weren't delivered until the late ‘forties.
It has been reported that 39 Nakajima A6M2-N “Rufe” floatplane fighters were supplied to the RTN with 12 being delivered in 1941 and 27 more following in 1942. These reports are without foundation. Two other types reported as having served with the Royal Thai Navy during World War II, Mitsubishi F1M2 “Pete” observation floatplanes and Tachikawa Ki-9 “Spruce” trainers, did not serve in any branch of the Royal Thai armed forces.
The Japanese aircraft in Royal Thai Air Force and Royal Thai Navy service were the most modern aircraft operated during World War II. Although combat and operational losses took their toll during World War II, the Japanese aircraft in Thai service were used until lack of spares, as well as wear and tear, forced their withdrawal from service. The last Japanese designed aircraft in Thai service were the Mitsubishi Ki-30s, Nakajima Ki-43s and, presumably, the Tachikawa Ki-55s, all of these types being withdrawn between 1949 and 1950. According to one credible source, the last remaining Japanese aircraft (three Ki-27bs and one Ki-43, all based at Don Muang), were withdrawn from use and scrapped because the US advisors were “displeased” that Japanese aircraft were still in service with the Royal Thai Air Force. The RTAF High Command then ordered the grounding and scrapping of the last Japanese aircraft. By that time, the Royal Thai Air Force had been largely re-equipped with American and British aircraft such as Grumman F8F Bearcats, N.A. T-6 Texans and Supermarine Spitfire XIV's. The air arm of the Royal Thai Navy was incorporated into the RTAF in 1951, after a failed coup d'etat.
The author wishes to extend his gratitude towards Steve Darke, who maintains the excellent web site www.thai-aviation.net and Vidya Tapasanan, for proofreading, and allowing the author to use information in his articles previously published in the Asahi Journal. Vidya Tapasanan has also supplied the photographs in this article. Finally, Edward M. Young, whose book “Aerial Nationalism” remains the best title on Thai aviation, and the inspiration for this article.