Initial states of Thailand

Before the southward migration of the Tai from Guangxi beginning in the 4th century, the Indochinese peninsula was already inhabited by Austronesians, who had spread into all subregions by approximately 30,000 BP. These populations left evidence of an early local culture known as the Hoabinhian, a term applied to a lithic industry and long-term cultural tradition characterised by stone tools and flaked cobble artefacts, which emerged around 10,000 BP in caves and rock shelters. First identified at sites in Hòa Bình, Vietnam, the Hoabinhian was later documented in Terengganu, Malaysia, Sumatra, Thailand, Laos, Myanmar, Cambodia, and Yunnan, southern China.

Austroasiatic Mon and Khmer groups, believed to have originated in northeastern India, predominately populated the riverine lowlands of Indochina from around 5,000 BP. Austronesian migrants later arrived along the coast of what is now central Vietnam around 2,500 BP.

The controversial Two layer hypothesis proposes a later migration of agricultural populations from the Yangtze River valley around 3,000 BP. These groups are thought to have introduced wet-rice and millet farming to mainland Southeast Asia.

The site of Ban Chiang in northeastern Thailand is regarded as the earliest known centre of copper and bronze production in Southeast Asia and has been dated to approximately 2000 BCE.

The earliest known records of a political entity in Indochina are associated with Funan, which was centred in the Mekong Delta and encompassed territories within present-day Thailand. Chinese annals attest to Funan's existence as early as the 1st century CE, while archaeological evidence indicates extensive human settlement in the region since at least the 4th century BCE.

The kingdoms of Langkasuka and Tambralinga on the Malay Peninsula appear in Chinese sources by the 5th century CE. Alongside Funan, these polities are commonly described as Indianized kingdoms, having adopted elements of Indian culture, religion, political organisation, administration, epigraphy, literature, and architecture following centuries of trade and socio-economic interaction with the Indian subcontinent.

The Mon Dvaravati principalities emerged during the middle of the first millennium CE in the lower Chao Phraya River valley of present-day central Thailand. Unlike Funan, Langkasuka, and Tambralinga, which were situated within the international trade network, Dvaravati remained comparatively isolated. Despite this, Mon–Dvaravati culture developed a sophisticated artistic and religious tradition rooted in Hindu cosmology. Distinctive stylistic features, such as the faceted mitre positioned high on the forehead and characteristic facial features—particularly the eyes—have continued to influence Thai sculpture.