Initially a group of small kingdoms, the ancient Khmer society of Cambodia was increasingly consolidated over the course of the sixth century. In the ninth century, Angkor emerged as the capital of a unified kingdom that, under a series of powerful kings, gradually expanded into an empire encompassing much of present-day Thailand, Laos, and Vietnam. Surrounding Angkor, a vast area of rice fields and the nearby Tonle Sap (Great Lake), with its abundance of fish, provided the economic basis for the flourishing empire. Angkor was attacked several times in the 14th and early 15th centuries, then finally abandoned as the Khmer capital was moved south to the area of Cambodia's modern capital, Phnom Penh.

Khmer Empire boundary
Present-day national boundaries