The region known today as Thailand has been inhabited by humans since the paleolithic period (about 10,000 years ago). Prior to the fall of the Khmer Empire in the 13th century, various states thrived there, such as the various Tai, Mon, Khmer and Malay kingdoms, as seen through the numerous archaeological sites and artifacts that are scattered throughout the Siamese landscape. Prior to the 12th century however, the first Thai or Siamese state is traditionally considered to be the Buddhist kingdom of Sukhothai, which was founded in 1238.
Following the decline and fall of the Khmer empire in the 13th – 14th century, various Buddhist Tai Kingdoms of Sukhothai, Lanna and Lan chang were on the ascendancy. However, a century later, Sukhothai’s power was overshadowed by the new kingdom of Ayutthaya, established in the mid-14th century.
After Ayutthaya fell in 1767 to the Burmese, Thonburi was the capital of Thailand for a brief period under King Taksin the Great. The current (Rattanakosin) era of Thai history began in 1782 following the establishment of Bangkok as capital of the Chakri dynasty under King Rama I the Great.
Siam retains an immemorial tradition of trade with its neighboring states and the cultures of the Indian ocean and the South China sea. European trade and influence arrived to Thailand in the 16th century, beginning with the Portuguese. Despite European pressure, Thailand is the only Southeast Asian nation never to have been colonised. Two main reasons for this were that Thailand had a long succession of very able rulers in the 1800s and that it was able to exploit the rivalry and tension between the French and the British. As a result, the country remained as a buffer state between parts of Southeast Asia that were colonized by the two colonial powers. Despite this, Western influence led to many reforms in the 19th century and major concessions, most notably being the loss of large territory on the east side of the Mekong to the French and the step by step absorption by Britain of the Shan (Thai Yai) States (now in Burma) and the Malay Peninsula. The loss initially included Penang and Tumasik and eventually culminated in the loss of three predominantly ethnic-Malay southern provinces, which later became Malaysia’s three northern states, under the Anglo-Siamese Treaty of 1909.
In 1932, a bloodless revolution resulted in a new constitutional monarchy. During World War II, following an invasion and brief resistance, Thailand became an ally of Japan while at the same time maintaining an active anti-Japanese resistance movement known as the Seri Thai. After the war, Thailand emerged as an ally of the United States. As with many of the developing nations during the Cold War, Thailand then went through decades of political transgression characterised by coups d’état as one military regime replaced another, but eventually progressed towards a stable prosperity and democracy in the 1980s.
In 1997, Thailand was hit with the Asian financial crisis and the Thai baht for a short time peaked at 56 baht to the US dollar compared to about 25 baht to the dollar before 1997. Since then, the baht has regained most of its strength and as of 23 May 2007, is valued at 32 baht to the US dollar.
The official calendar in Thailand is based on Eastern version of the Buddhist Era, which is 543 years ahead of the Gregorian (western) calendar. For example, the year AD 2008 is called 2551 BE in Thailand.