I think a large clue we may be overlooking is the button with the multi barrel gun. I did a comparison on google with various guns and the gun on the button looks very much like a Gatling gun.
Then it was just a matter of searching the history of the Gatling gun and it looks like Wikipedia may have the answers.
'By 1880 Siam had imported an unknown number of Gatling's. By 1885 the kingdom had a Gatling Gun regiment of 600 men; those weapons were possibly used in the Haw Wars. They were also seen among Prince Bigit's escort in 1886'
ref. Heath, Ian (2003) [1998]. Armies of the Nineteenth Century: Burma and Indo-China. Foundry Books. p. 155. ISBN 978-1-90154-306-3.
So it appears Siam (Thailand) may be the source of these buttons
Link to image showing Siamese troops with Gatling gun during Haw wars:
https://en.wikipedia.org/wiki/File:A...ars_(1875).jpg