Excavations at four Iron Age moated sites in the Mun Valley in Thailand have identified seminal innovations, defined as emergent properties, that illuminate the origins of the kingdom of Angkor. Combined with recent research at Angkor itself, they present a compelling case for re-examining fundamental cultural changes that took place over a period of little more than four centuries, from AD 400–800. They compare with similarly rapid developments in Mesoamerica and Mesopotamia; fundamental parallels are evident in the role of charismatic agents for change, an ideology conferring god-like status on leaders, a new and highly productive economic base, an expanded interaction sphere for the exchange of prestige goods, and endemic warfare.