Thailand (/ TY-land or / TY-lənd; Thai: ประเทศไทย, RTGS: Prathet Thai, pronounced [pratʰêːt tʰaj] (listen)), officially the Kingdom of Thailand (Thai: ราชอาณาจักรไทย, RTGS: Ratcha-anachak Thai [râːtt͡ɕʰaʔaːnaːt͡ɕàk tʰaj] (listen), Chinese: 泰国), formerly known as Siam (Thai: สยาม, RTGS: Sayam [sajǎːm]), is a country at the centre of the Indochinese peninsula in Southeast Asia.
Etymology of "Siam"
The country has always been called Mueang Thai by its citizens. By outsiders prior to 1949, it was usually known by the exonym Siam (Thai: สยาม RTGS: Sayam, pronounced [sajǎːm], also spelled Siem, Syâm, or Syâma). The word Siam may have originated from Pali (suvaṇṇabhūmi, “land of gold”) or Sanskrit श्याम (śyāma, “dark”) or Mon ရာမည(rhmañña, “stranger”). The names Shan and A-hom seem to be variants of the same word. The word Śyâma is possibly not its origin, but a learned and artificial distortion. Another theory is the name derives from Chinese: "Ayutthaya emerged as a dominant centre in the late fourteenth century. The Chinese called this region Xian, which the Portuguese converted into Siam." (Baker and Phongpaichit, A History of Thailand, 8)
A further possibility is that Mon-speaking peoples migrating south called themselves 'syem' as do the autochthonous Mon-Khmer-speaking inhabitants of the Malay Peninsula.
The signature of King Mongkut (r. 1851–1868) reads SPPM (Somdet Phra Poramenthra Maha) Mongkut Rex Siamensium (Mongkut King of the Siamese), giving the name "Siam" official status until 24 June 1939 when it was changed to Thailand. Thailand was renamed to Siam from 1946 to 1948, after which it again reverted to Thailand.
Etymology of "Thailand"
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". A famous Thai scholar argued that Thai (ไท) simply means "people" or "human being", since his investigation shows that in some rural areas the word "Thai" was used 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' through the following chain: *kəri: > *kəli: > *kədi:/*kədaj > *di:/*daj > *dajA (Proto-Southwestern Tai) > tʰajA2 (in Siamese and Lao) or > tajA2 (in the other Southwestern and Central Tai languages classified by Li Fangkuei). Michel Ferlus' work is based on some simple rules of phonetic change observable in the Sinosphere and studied for the most part by William H. Baxter (1992).
While Thai people will often refer to their country using the polite form prathet Thai (Thai: ประเทศไทย), they most commonly 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) -chak (from Sanskrit चक्र cakra- "wheel", a symbol of power and rule). The Thai National Anthem (Thai: เพลงชาติ), written by Luang Saranupraphan during the extremely 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 the unity of Thai flesh and blood."