The Khmer Empire was at its apogee during the reign of Jayavarman VII (1181-1215 A.D.). Its territory covered the current Cambodia, all of southern Vietnam, all of the current Laos, all of the current Thailand, and part of the current Malaysia. Unlike the Khmers, Thais, known then as Siameses, were not natives of the region. The kingdom of Thailand, known then as Siam, did not appear in Southeast Asia until the mid- 14th century.