The cultural roots of the present-day Lao lie in Indian civilization , not Chinese. From the first century AD, Indian traders began introducing Buddhism to Southeast Asia, and between the sixth and ninth centuries upper Laos, along with central and northeastern Thailand, was dominated by the Theravada Buddhist culture of the Mon people, known as Dvaravati .

As the ninth century drew to a close, Dvaravati's influence was rapidly being eclipsed by the Khmer Empire of Angkor. At its height, the mostly Hindu Khmer Empire extended from its core of Cambodia and lower northeastern Thailand into Vietnam, central Thailand and Laos, where it built dozens of Angkor-style temple complexes.