While it has been modified to suit the warmer climate, I am fairly sure that it was based on a Western template. The folded collars, the shoes, etc. are dead giveaways.
This goes back to:
https://en.wikipedia.org/wiki/History_of_Thai_clothing#Modern_RattanakosinFrom the 1860s onward, Thai royals "selectively adopted Victorian corporeal and sartorial etiquette to fashion modern personas that were publicized domestically and internationally by means of mechanically reproduced images."[11] Stitched clothing, including court attire and ceremonial uniforms, were invented during the reign of King Chulalongkorn.[11] Western forms of dress became popular among urbanites in Bangkok during this time period.[11] During the early 1900s, King Vajiravudh launched a campaign to encourage Thai women to wear long hair instead of traditional short hair, and to wear pha sinh (ผ้าซิ่น), a tubular skirt, instead of the chong kraben (โจงกระเบน), a cloth wrap.[12]
...
On 15 January 1941, Plaek Pibulsonggram issued a Thai cultural mandate to modernize and westernize Thai dress, by deeming long-practiced customs of wearing underpants, wearing no shirt, or wearing a wraparound cloth, as forms of inappropriate public attire.[13]
This is what we are here to reverse.
At least the uniform shown does not include neckties! That is the only good thing about it.