Pre-Thai Kingdoms

Over the centuries leading up to the era of recorded history, Thailand was first peopled by Mon and Khmer groups and later by the Tai, an ethnic group that migrated from southern China to Vietnam and gradually into Laos and northern Thailand.
In the first millennium of the Common Era, Tai people had dispersed across Yunan, Vietnam, Laos, Thailand, and Myanmar fragmenting into various linguistic sub-sects. Relatively minor players in the region throughout this period, the Tai inhabited the northernmost reaches of Southeast Asia, sandwiched between the kingdoms of Nan Zhao, Pyu, and Angkor.
Beginning in around the 2nd century CE, the Srivijaya Empire of Sumatra expanded its reach up the Malaysian Peninsula into southern Thailand. Nakhon Si Thammarat and Chiaya, Surat Thani were founded during this period to facilitate trade across the Isthmus of Kra.
Around the 6th to the 9th centuries, the fertile central plains were inhabited by a Mon civilization known as Dvaravati. Distinct from its neighboring kingdoms of Chenla and Angkor, Dvaravati remains a mysterious civilization that established cities surrounded by moats and earthen walls, with Lopburi serving as an important religious center and Nakhon Pathom near Bangkok possibly its ‘capital’. While much is unknown about this realm, the Dvaravati had well established internal and external trading routes that were important to the development of Thailand and left a wealth of Buddhist artwork that testifies to the great influence Indian culture and religion had on the region.
From the 9th to the 11th centuries the Khmers of Angkor expanded their kingdom to include most of modern-day Thailand, with important provincial cities established at Phimai, Lopburi and even Nakhon Si Thammarat. Over several centuries many facets of the Khmer culture were imposed on/absorbed by the native population, which was becoming increasingly Tai as those populations migrated south. The temples at Phanom Rung, Phimai, and Lopburi are enduring testaments to this period of Thai history.
Throughout the reign of Angkor, Lopburi often asserted its independence and was clearly an important center for burgeoning Syam culture. The Chinese, who referred to emissaries from the region as representing “Hsien” or Siam (as it was apparently pronounced) documented a request from Lopburi requesting independence from Angkor as early as 1001.
In northern Thailand, Buddhist scholars from Lopburi founded a city-state known as Haripunjaya in Lamphun, northern Thailand around the 9th century (a Mon enclave that remained independent until the 13th century). Elsewhere in the north, the Tai people were fanning out and establishing their own city states, notably at Chiang Saen, where one of the first powerful Thai kingdoms, Lan Na, was originally established in the 12th century. The establishment of Lan Na, Sukhothai, and Phayao, three allied kingdoms founded by contemporary leaders, represents the beginning of the Thai history as we know it.