The region of nowaday Thailand has been inhabited by human beings since paleolithic period (about 500,000 - 10,000 years ago). Due to its geographical location, Thai culture has always been greatly influenced by India and China as well as the neighboring cultures of Southeast Asia. However, the first Thai or Siamese state is traditionally considered to be the Buddhist kingdom of Sukhothai was founded in 1238, followed by the decline and fall of the Khmer empire in the 13th - 15th century AD.

A century later, Sukhothai's power was overshadowed by the larger Siamese kingdom of Ayutthaya, established in the mid-14th century. After the sack of Angkor by the Siamese armies in 1431, much of the Khmer court and its Hindu customs were brought to Ayuthaya, and Khmer customs and rituals were adopted into the courtly culture of Siam.

After Ayuthaya fell in 1767 to the Burmese, Thonburi was the capital of Thailand for a brief period under King Taksin the Great. The current (Ratthanakosin) era of Thai history began in 1782 following the establishment of Bangkok as capital of the Chakri dynasty under King Rama I the Great.

European powers began travelling to Thailand in the 16th century. Despite European pressure, Thailand is the only Southeast Asian country never to have been colonised by a European power. The two main reasons for this is 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 colonised by the two European colonial powers. Despite this, Western influence led to many reforms in the 19th century and major concessions to British trading interests. This included the loss o the three predominantly ethnic Malay southern provinces, which later became Malaysia's three northern states. However, another ethnic Malay province named Pattani, now subdivided further into four smaller districts, has remained as Siamese territory to this day.