Siam / Thai porcelain gaming token - rectangular, small

World Coins - Siam / Thai porcelain gaming token - rectangular, small
zoom view
12mm x 16mm
 
If you collect these at all there is an old reference work by Ramsden, and it is:
Siamese Porcelain and Other Tokens , by H. A. Ramsden, F.R.N.S (1911), 57 pages.
 
You can sometimes locate the 1970s reprint.
 
These were in use in the 19th century and beyond at times.