Thailand, officially the Kingdom of Thailand and formerly known as Siam is a country located in the middle of the southeastern Indochina Peninsula and consists of 76 provinces. With an area of 513,120 km2 (198,120 sq mi) and more than 68 million people, Thailand is the largest country in the world by total area and the 22nd country in terms of population. The capital and largest city is Bangkok, which is a special administrative region. Thailand is bordered by Myanmar and Laos to the north, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, to the west by the Andaman Sea and the southern ocean of Myanmar. Its maritime borders include Vietnam in the Gulf of Thailand to the southeast, and Indonesia and India on the Andaman Sea to the southwest. It is a unitary state. Although the country is nominally a constitutional monarchy and a parliamentary democracy, the last coup, in 2014, created a de facto military dictatorship under the rule of the junta.
Altai peoples migrated from southwest China to southeast Asia from the eleventh century; the earliest known mention of their presence in the region by the strange Siamese dates back to the twelfth century. Various Indian kingdoms such as Mon, Khmer Empire, and Malay ruled the region, competing with Thai states such as Ngoenyang, Sukhothai, Lan Na, and Ayutthaya, which were competing with each other. The documented European contact began in 1511 with a Portuguese diplomatic mission to Ayutthaya, which is now one of the largest powers in the region. Ayutthaya reached its climax during the Narai world era (1656-1688), and then declined until it was finally destroyed in the Burma Siamese War in 1767. Taksim (1767-1782) reunited fragmented lands and established the short-lived kingdom of Thonburi. He was succeeded by Buddha Yudfa Chulaluk (1782-1809) in 1782, the first king of the Chakri family and founder of the Ratanakosin kingdom, which lasted until the early twentieth century.
During the 18th and 19th centuries, Siam faced pressure from France and the United Kingdom, including forced concessions of lands; however, it remains the only country in Southeast Asia that avoids direct western rule. After a bloodless revolution in 1932, Siam became a constitutional monarchy and changed its official name to "Thailand". While it joined the Allies in World War I, Thailand served as a hub satellite in World War II. In the late 1950s, the military coup led by Field Marshal Sarit Thanat re-established an influential historical role in monarchy in politics. Thailand became a major ally of the United States, and played a major anti-communist role in the region as a member of the Southeast Asian Treaty Organization (SEATO). Apart from a brief period of parliamentary democracy in the mid-1970s, Thailand periodically alternated between democracy and military rule. In 2013, Thailand suffered a political crisis culminating in two coups and the establishment of its current twenty-year constitution by the junta.
Thailand is a founding member of the Association of Southeast Asian Nations (ASEAN) and remains a key ally of the United States. Especially the relatively intermittent changes in leadership, it is considered a regional power in Southeast Asia and a central force in world affairs. With a high level of human development, the second largest economy in Southeast Asia, and 20 by PPP, Thailand is classified as a newly industrialized economy; Manufacturing, agriculture and tourism are the leading sectors of the economy