Third-party organic certification is prohibitively expensive for smallholder organic farmers supplying local markets and participatory guarantee systems (PGS) provide an attractive certification alternative. However, fewer farmers than expected have joined PGS initiatives, so domestic markets remain inadequately supplied. This study identifies how public policies, institutional arrangements, and market dynamics create systemic enablers and barriers to conversion to PGS certified organic vegetable production in Thailand. We pay particular attention to the role of state institutions and the emerging National Organic PGS Council in shaping opportunities for, and constraints on, PGS development. Using the Innovation System Performance Matrix, we examine how knowledge systems, political structures and institutions, and markets interact to influence PGS participation in Thailand. We found that state actors and the National Organic PGS Council support PGS development through training programmes, legal recognition, and coordination. However, fragmented mandates, limited PGS‑specific advisory services, and competing policies create significant barriers. Furthermore, the specific ways in which state institutions intervene in PGS ecosystems are central to explaining why PGS uptake remains limited, despite ambitious national organic action plans. These results can contribute to increasing the supply of organic vegetables in Southeast Asia by informing strategies to overcome the identified challenges.
Lormphongs et al. (Sat,) studied this question.