A country of southeast Asia on the Gulf of Thailand (formerly the Gulf of Siam), an arm of the South China Sea. Various Thai kingdoms were founded from the 13th century on, frequently coming into conflict with neighboring Burmese and Cambodian powers. Siam remained an absolute monarchy until 1932, when the king was compelled to accept a constitution, and the country was renamed Thailand in 1939. Thailand was occupied by the Japanese in World War II, and most of its numerous postwar governments were controlled by the military. Bangkok is the capital and the largest city.