The Khmer Empire had its beginnings in 790 when King Jayavarman conquered the Kingdom of Kambuja, until then under the Joke of the Javanese. The consecration rites of Jayavarman on Mount Julen [ now in Cambodia ] in 802 formalised the freeing of Kambuja from Java and the introduction of the Hindu cult of the Devaraja [ God King ] Hariharalaya was the name of the first settlement of the new Angkor Kingdom and by 889 this Khmer Empire held control as far as Ubon in Thailand.

The Khmer had a presence in Central, East, some parts of the North and the Northeast of Thailand [  I 'san ] since the second half of 6^th C. This presence lasted until the mid 13^th C. However the influences of Khmer styles, inspiration and iconography continued long after. Where the Khmer were and when can be traced from looking at the many stone inscriptions found throughout Thailand. These are dated by the alphabet used, which was either ancient Khmer, Pallava, Later Pallava, or Khmer and the language used which was either Pali, Sanskrit [ both from India ] and Khmer.

Khmer presence can also be traced by art objects and architecture ruins found in ancient sites. Scholars of art can classify art objects by their subject matter and style such that they can be dated precisely. The principal periods are the Pre-Angkor Period of   547-807  which include 5 distinct and consecutive time periods, and the Angkorian Period 827-1237 which includes 10 distinct and consecutive periods. Thus monuments and sculptures distributed in these parts of Thailand are dated.