Monarchy has thrived in five countries of Southeast Asia, blending traditions of kingship from the pre-colonial era with modern forms of constitutional rule. Brunei, Thailand, Malaysia, and Cambodia have monarchs as titular heads of state; Indonesia uniquely has forms of monarchy that thrive in a republican context at the regional level. These two traditions of monarchy, one archaic and the other modern, coexist uneasily—especially in times of stress, whether because of succession or political instability. Therefore, to understand the dynamics of political stability in Thailand and Malaysia, the role of monarchs cannot be ignored.