Originally Posted by allthai

This is a very good question.

The Thai people originated from Yunnan Province in China. They were know as the Tai or Dai people. People in Thailand today call them Tai Yai. This all happened starting around 1450 years ago.

The earliest written record from a Thai Kingdom dates back to the late 13th century. A slate from Sukho-thai dated 1292 AD bears the earliest known inscription in the Thai language.

At that time the Siamese written word for the Tai people who migrated to Siam was Dtai. When the name Siam was changes to Thailand in the late 1940's they had to figure a way to spell it as there is no English for the dt in Dtai so for English they changed it to th, which is now Thailand.

Many signs today if you see the Thai character "Dor Dtao", which is the dt, in English is written with th as a replacement. To make it even more confusing dt or "Dor Dao" is not used in the Thai spelling of Thailand, go figure.

Hope that makes sense,
Randy and Ning