Thailand was heavily influenced by the culture and religions of India, starting with the Kingdom of Funan from around the 1st century CE to the Khmer Empire. Thailand in its earliest days was under the rule of the Khmer Empire, which had strong Hindu roots, and the influence among Thais remains even today.
After the fall of the Khmer Empire in the 13th century, states established by the Tai peoples, Mons, Khmers, Chams and Ethnic Malays, began to flourish in the area. Before the 12th century, the first Siamese state is considered to be the Buddhist Sukhothai Kingdom, founded in 1238. Following the decline and fall of the Khmer empire in the 13th–15th century, the Buddhist Tai kingdoms of Sukhothai, Lanna, and Lan Xang (now Laos) were on the rise. However, a century later, the power of Sukhothai was overshadowed by the new Kingdom of Ayutthaya, established in the mid-14th century in the lower Chao Phraya River. After the fall of Ayutthaya in 1767 to the Burmese, the capital moved to Thonburi for 15 years. 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.
Thailand is the only Southeast Asian nation to never have been colonised. In 1896, Britain and France guaranteed of the Chao Phraya valley as their buffer state, while the remaining parts of Southeast Asia were colonised by the west.
In 1939, the name of the kingdom was changed to "Thailand".