Thailand, officially the Kingdom of Thailand (Prathet Thai, or “Land of the Free”), country in Southeast Asia. Thailand is the only Southeast Asian country never to have been occupied by any European or other foreign power, except in war. The country was an absolute monarchy from 1782 until 1932, when rebels seized power in a coup and established a constitutional monarchy. Since then, Thailand has come under the rule of many governments, both civil and military. The country was known as Siam until 1939 (when it was renamed Thailand), and again for a few years in the late 1940s. In 1949 the name Thailand was adopted a second time.

Central Thailand is dominated by a large fertile plain, formed by the country’s chief river, the Chao Phraya, and its tributaries. Much of the country’s rice and other crops are grown in this region. Mountains and plateaus surround the central plain on the west, north, and east. The western mountain ranges extend south onto the Malay Peninsula (Malaya). Bangkok, located on the Chao Phraya near the Gulf of Thailand, is Thailand’s capital and largest city.