AbstractDrawing upon institutional theory, sustainability scholars have demonstrated that various institutional factors, such as environmental regulations, national business systems, and global sustainability standards, shape legitimate sustainability frameworks. However, most of the studies have focused on formal institutions that have law‐like regulations and procedures. Owing to the skewed attention, the role of informal institutions in shaping sustainability frameworks has remained largely unexplored. The present study suggests that an informal institution, particularly religion, can play a significant role in developing a locally driven sustainability framework. In particular, this study investigates Thai context where Buddhism has shaped people's mindset, moral principles and day‐to‐day economic activity. For the past few decades, Thailand has theorized its own unique sustainability framework—sufficiency economy philosophy—based on Buddhist worldview on interrelationships of economy, society, and environment. By shedding light on how religion is formalized as a sustainability framework, this research contributes to institutional approach to sustainability.