Japanese Aircraft in Royal Thai Air Force and Royal Thai Navy Service During World War II
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 308th 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 25th 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 1st 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.