In the summer of 1943, the Japanese Army gave "Hayabusa" fighters to the Royal Thai Airforce to help in the defence of the area. 24 of them were given to the 1st Hikodan. Upon arrival, the 15th Hiko Chutai was organised, equipped exclusively with these aircraft and was based at Don Muang airfield (Don Mueang) of Bangkok responsible for the air defence of the capital.
A number of "Hayabusa" were also given to the 16th Hiko Chutai based at Lampang in the North of Thailand as replacements to their older Nakajima Ki-27s "Nate".
A photo from a vintage publication showing a Japanese (left) and a Thai pilot discussing their flight route. Note the camouflage pattern.
Below is a short clip from the NHK collection showing the arrival of the new fighters at Don Muang and how the Thai markings were applied.
Here's a translation of the Japanese script.
"A white elephant flag is drawn on the tail. Let's intercept the enemy planes that are attacking Thailand and protect our skys by ourselves. Under the guidance of the brave soldiers of the Japanese Imperial Army, Thai Air Force officers will work diligently to improve their flight skills with "Hayabusa" fighters and special training. They will join hands with Japan and fight together in the Greater East Asia War.
Enemy planes: come if you dare. With a series of enthusiastic training, the Thai defense camp is steadily getting stronger."
Note the different camouflage pattern with the aircraft in the top photo. The aircraft in the stills does not seem to have any previous unit markings.
A line-up of new "Hayabusa" being inspected by Japanese and Thai pilots. Note that the aircraft in the foreground seems to have a centrally attached drop tank.
The exhaust indicates that this is a Nakajima Ki-43 Model II and from the camouflage pattern we can conclude that it is probably the same aircraft in the two stills at the top.
I think this is the same "Hayabusa" with the one in the above stills. As you will notice in the clip, it has hinomaru on the wings. These were later erased and the Thai markings were applied together with camouflage.
Below are more photos of Thai "Hayabusa" fighters with Japanese and Thai pilots and crews.
The first photo is very similar to the one at the top of the page, so it's safe to assume it was taken about the same time.
The photo below is often reproduced, but most times in very bad quality. Note that the top camouflage continues a little under the wing leading edge. Also note the removed hinomaru and the Thai insignia painted over it.
There are many illustrations of Thai "Hayabusa" on the net, most of very bad quality, and the camouflage pattern has been depicted very inaccurately.
Below is an illustration by Nohara Shigeru featured in Model Art #395. In my opinion, it shows fairly accurately the aircraft seen in the top and the photos above.
And below is an illustration by Koizumi Kazuaki included in an old Koku Fan issue, depicting the aircraft in the clip.
The above, only the stills, was originally posted in 2012 and received basically no reaction. Since then, the photos have been ofcourse "borrowed" by various blogs without any credit. Thank you guys for the support!