Southeast Asia included the Pagan Kingdom, the Khmer Empire, Vietnam, and Trading Kingdoms. The Pagan Kingdom began in about 840. Their first great king was Anawrahta, he ruled from 1044 to 1077. Under his ruled they built thousands of Buddhist temples. Vietnam, unlike most of southeast Asia, was influenced more by China. In 11 BC the Han dynasty took over Vietnam, this is why the Vietnamese have so many cultural aspects of China.
Rice Cultivation was popular in Southeast Asia due to the need for rice as a crop, and the perfect climate was available.