The first recorded kingdom attributed to the Mon people is Dvaravati,^[15] which prospered until around 1000 CE when their capital was sacked by the Khmer Empire and a significant portion of the inhabitants fled west to present-day Lower Burma and eventually founded new polities. Another Mon-speaking state Haripuñjaya also existed in northern Thailand down to the late 13th century.^{[16 ]}

According to the colonial era scholarship, as early as the 6th century, the Mon began to enter the present-day Lower Burma from the Mon kingdoms of Haribhunjaya and Dvaravati in modern-day Thailand. By the mid 9th century, the Mon had founded at least two small kingdoms (or large city-states) centred around Bago and Thaton. The states were important trading ports between Indian Ocean and mainland Southeast Asia. Still, according to traditional reconstruction, the early Mon city-states were conquered by the Pagan Kingdom from the north in 1057, and that Thaton's literary and religious traditions helped to mould early Pagan civilisation.^[17] Between 1050 and about 1085, Mon craftsmen and artisans helped to build some two thousand monuments at Pagan, the remains of which today rival the splendors of Angkor Wat.^[18] The Mon script is considered to be the source of the Burmese script, the earliest evidence of which was dated to 1058, a year after the Thaton conquest, by the colonial era scholarship.^[19]

However, research from the 2000s (still a minority view) argues that Mon influence on the interior after Anawrahta's conquest is a greatly exaggerated post-Pagan legend, and that Lower Burma in fact lacked a substantial independent polity prior to Pagan's expansion.^[20] Possibly in this period, the delta sedimentation — which now extends the coastline by three miles (4.8 kilometres) in a century — remained insufficient, and the sea still reached too far inland, to support a population even as large as the modest population of the late precolonial era. The earliest evidence of Burmese script is dated to 1035, and possibly as early as 984, both of which are earlier than the earliest evidence of the Burma Mon script (1093). Research from the 2000s argues that the Pyu script was the source of the Burmese script.^[21]

Though the size and importance of these states are still debated, all scholars accept that during the 11th century, Pagan established its authority in Lower Burma and this conquest facilitated growing cultural exchange, if not with local Mon, then with India and with Theravada stronghold Sri Lanka. From a geopolitical standpoint, Anawrahta's conquest of Thaton checked the Khmer advance in the Tenasserim coast.^[20]