Ancient History of ThailandFacts and Details. The formal name of Thailand is Kingdom of Thailand (Ratcha Anachak Thai). The term for citizen(s) is Thai (singular and plural). By some translations Thailand means "Land of the Free" (Prathet Thai ) and this is an apt name for this country where anything goes. By other translations it simply means “Land of the Thais.” The Thais call their country “Muang Thai,” which also means “Land of the Free.” They call themselves the “Khon Tha,” which means “free people.” “Siam” and “Siamese” are terms mainly used by foreigners.