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 a parliamentary democracy with a constitutional monarchy currently headed by King Rama IX, the ninth king of the House of Chakri, who has reigned since 1946 as the world's longest-serving current head of state and the country's longest-reigning monarch. The King of Thailand's titles include Head of State, Head of the Armed Forces, Adherent of Buddhism, and Upholder of religions.With a total area of approximately 513,000 km2, Thailand is the world's 51st-largest country. It is the 20th-most-populous country in the world, with around 65 million people. The capital and largest city is Bangkok, which is Thailand's political, commercial, industrial and cultural hub. About 75–85% of the population is ethnically Tai, which includes four major regional groups: Central Thai: 30%; Northeastern Thai: 22%, Northern Thai: 9%; and Southern Thai: 7%. Thai Chinese, those of significant Chinese heritage, are 14% of the population, while Thais with part-Chinese ancestry comprise up to 40% of the population. Thai Malays represent 3% of the population, with the remainder consisting of Mons, Khmers and various "hill tribes". The country's official language is Thai and the primary religion is Buddhism, which is practised by around 95% of the population.Thailand experienced rapid economic growth between 1985 and 1996, becoming a newly industrialized country and a major exporter. Manufacturing, agriculture, and Tourism are leading sectors of the economy. Among the ten ASEAN countries, Thailand ranked second in the 2014 United Nations Human Development Index, which measures quality of life according to areas such as life expectancy and income. Its large population and growing economic clout have made it a middle power in the region and around the world.