Iron-production sites of the early historic period in Mainland Southeast Asia (fifth to fifteenth centuries AD) are rare. Recent excavations at the Tonle Bak site in central Cambodia now provide the first evidence for furnace technology, metallurgical characteristics of slag concentrations and evidence for the organisation of local smelting communities and ritual practices during the peak of the Angkorian Khmer Empire. The results demonstrate that the smelters were directly integrated with Angkorian state-exchange networks. They also raise questions about the use of ethnohistorical records for understanding the identity and organisation of these early metalworkers.