Thailand, officially the Kingdom of Thailand, formerly known as Siam, is a country located at the centre of the Indochina peninsula in Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia and to the west by the Andaman Sea and the southern extremity of Burma. Its maritime boundaries include Vietnam in the Gulf of Thailand to the southeast, and Indonesia and India in the Andaman Sea to the southwest. Thailand is the 21^st-most-populous country, with around 64 million people. The capital and largest city is Bangkok. The country is a constitutional monarchy, headed by King Rama IX, the ninth king of the House of Chakri, who, having reigned since 1946, is the world’s longest serving head of state and the longest-reigning monarch in Thai history.