I believe it was King Rama who freed the slaves, though. In his day (about 150 years ago) 99% of the people in Thailand were slaves.
There are the "Overseas Chinese" who are a phenomenon with its origins in the founding of a Chinese navy port at Penang Island in the early 1400s by Admiral Zheng He (known to the West as Sinbad the Sailer Man).
This guy may well have discovered and mapped the Americas.
If you come to Thailand, don't say that to an ethnic Thai because you will probably get into a fight. The cultures are still quite different.