Iron was worked by about 500 BC, with supporting evidence coming from the Khorat Plateau, in modern-day Thailand. In Cambodia, some Iron Age settlements were found beneath Baksei Chamkrong and other Angkorian temples while circular earthworks were found beneath ''Lovea'' a few kilometres north-west of Angkor. Burials, much richer than other types of finds, testify to improvement of food availability and trade (even on long distances: in the 4th century BC trade relations with India were already opened) and the existence of a social structure and labour organisation.