Thailand
Etymology

Thailand was known by outsiders prior to 1939 as Siam. According to George Cœdès, the word Thai (ไทย) means 'free man' in the Thai language, "differentiating the Thai from the natives encompassed in Thai society as serfs". According to Chit Phumisak, Thai (ไท) simply means 'people' or 'human being'; his investigation shows that some rural areas used the word "Thai" instead of the usual Thai word khon (คน) for people. According to Michel Ferlus, the ethnonyms Thai-Tai (or Thay-Tay) would have evolved from the etymon *k(ə)ri: 'human being'.

Thais often refer to their country using the polite form prathet Thai (Thai: ประเทศไทย). They also use the more colloquial term mueang Thai (Thai: เมืองไทย) or simply Thai; the word mueang, archaically referring to a city-state, is commonly used to refer to a city or town as the centre of a region. Ratcha Anachak Thai (Thai: ราชอาณาจักรไทย) means 'kingdom of Thailand' or 'kingdom of Thai'. Etymologically, its components are: ratcha (Sanskrit: राजन्, rājan, 'king, royal, realm'), ana- (Pali āṇā 'authority, command, power', itself from the Sanskrit आज्ञा, ājñā, of the same meaning), and -chak (from Sanskrit चक्र cakra- 'wheel', a symbol of power and rule). The Thai National Anthem (Thai: เพลงชาติ), written by Luang Saranupraphan during the patriotic 1930s, refers to the Thai nation as prathet Thai (Thai: ประเทศไทย). The first line of the national anthem is: prathet thai ruam lueat nuea chat chuea thai (Thai: ประเทศไทยรวมเลือดเนื้อชาติเชื้อไทย), 'Thailand is founded on blood and flesh'.

The former name Siam may have originated from Sanskrit श्याम (śyāma, 'dark') or Mon ရာမည (rhmañña, 'stranger'), probably the same root as Shan and Assam. The word Śyâma is possibly not the true origin, but a pre-designed deviation from its proper, original meaning. Another theory is the name derives from the Chinese calling this region 'Xian'. The ancient Khmers used the word Siam to refer to people settled in the west Chao Phraya River valley surrounding the ancient city of Nakhon Pathom in the present-day central Thailand; it may probably originate from the name of Lord Krishna, which also called Shyam, as in the Wat Sri Chum Inscription, dated 13th century CE, mentions Phra Maha Thera Sri Sattha came to restore Phra Pathommachedi at the city of Lord Krishna (Nakhon Pathom) in the early era of the Sukhothai Kingdom.

The signature of King Mongkut (r. 1851–1868) reads SPPM (Somdet Phra Poramenthra Maha) Mongkut Rex Siamensium (Mongkut, King of the Siamese). This usage of the name in the country's first international treaty gave the name Siam official status, until 24 June 1939 when it was changed to Thailand. Thailand was briefly renamed Siam from 1946 to 1948, after which it again reverted to Thailand.
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