Revenue stamps were introduced the first time in Thailand in 1883.
The first series were Agriculture stamps for rice paddy tax and a set of 5 stamps, showing King Rama 5, to be used as as Court Fee Stamps.
Also starting around that time, Thailand desperately tried not to be colonized. In was threatened in the east by the French in Indochina and in the West and South by the British in Burma and Malaya.
It was successful in staving off colonialization, but lost in the process, lots of land in the South and East part of the country.
On of the means to success was trying to modernize Thailand and its governing systems.
King Rama 6 (1910-1925) established a miniature city, with small scale buildings, located in the Amphorn Palace gardens. Below page is a write up. Shown is a receipt with a small blue stamp (smallest stamp ever issued and fitting with a miniature city).
Note, this stamp was not issued by the postal authorities but was specially made for the king.
This receipt purchased some 8 years ago would easily sell now for more than $3,500