The official name of Thailand is Kingdom of Thailand. In Thai language, it’s called Prathet Thai. (Prathet means country). Around until 1939, the country was known as “Siam” and then it was changed to tire current name, “Prathet Thai”, or “Thailand” once. However, it was renamed back to “Siam” from 1945 to 1949, then back to “Thailand” on May 11,1949.”Thai” means “free”, therefore, “Thailand” means “Land of the Free.”It must show their pride about the fact that Thailand is the only one country that has never been colonized in Southeast Asia while other countries around were colonized by Great Britain and France.Kingdom of Thailand Famous Places Pictures..