His research at the Bronze Age sites of Ban Non Wat has shown that the initial Bronze Age in this part of Southeast Asia began in the 11th century BCE. With his son, Thomas, professor of archaeological science at Oxford University, he has re-dated the site of Ban Chiang, showing that there too, contrary to claims from the University of Pennsylvania, bronze casting also began in the 11th century BCE. His current research involves excavations at the Iron Age site of Non Ban Jak. There, he has identified for the first time in Thailand, an extensive area comprising the residential quarter of an Iron Age town, complete with houses, a lane, an iron working area and several ceramic kilns. In conjunction with many colleagues, he has linked a period of increased aridity with the start of an agricultural revolution that stimulated the rise of early states.