It became a newly industrialised country and a major exporter in the 1990s.
Thailand was renamed Siam from 1945 to , after which it again reverted to Thailand.
According to George Cœdès, the word Thai (ไทย) means "free man" in the Thai language, "differentiating the Thai from the natives encompassed in Thai society as serfs.") means "kingdom of Thailand" or "kingdom of Thai".
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 or Menam area.
Ayutthaya's expansion centred along the Menam while in the northern valleys the Lanna Kingdom and other small Tai city-states ruled the area.
Prior to the 12th century however, the first Thai or Siamese state is traditionally considered to be the Buddhist Sukhothai Kingdom, which was 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.
The word Śyâma is possibly not its origin, but a learned and artificial distortion.
Another theory is the name derives from Chinese: "Ayutthaya emerged as a dominant centre in the late fourteenth century.
Additionally, "the Mongols, after the seizure of Ta-li on January 7, 1253 and the pacification of Yunnan in 1257, did not look with disfavor on the creation of a series of Thai principalities at the expense of the old Indianized kingdoms." The Menam Basin was originally populated by the Mons, and the location of Dvaravati in the 7th century, followed by the Khmer Empire in the 11th.
The History of the Yuan mentions an embassy from the kingdom of Sukhothai in 1282.
Ayutthaya became one of the most vibrant trading centres in Asia.