Understanding how indigenous people manage their natural resources can provide a basis for formulating appropriate policies for natural resources management that benefits them while preserving their cultural beliefs. The objective of this study is to investigate the factors that influence the management of natural resources and the conservation of river ecology by the indigenous people in the Nongchaiwan wetland. We conducted in-depth interviews with 5 key informants and quantitative surveys with 158 households in two phases over a period of 3 years. Ancestral spiritual beliefs that are still salient in the Lower Songkhram River Basin influence natural resources management because they traditionally link people and natural resources. Such spiritual beliefs in the Lower Songkhram River Basin supported the indigenous people to continue conserving the natural resources in their territory. In addition, property rights granted to indigenous people also contribute to the conservation of natural resources. Our findings suggest that policy makers should engage with local beliefs in order to achieve sustainable resource management and, therefore, such practices should be recognized and included in the government’s policies on natural resources management in locations, where indigenous people live for generations.