Résumé
The rapid expansion of oil palm cultivation in the humid tropics has raised major sustainability concerns. Certification systems, notably the Roundtable on Sustainable Palm Oil (RSPO), aim to promote transparency and accountability in supply chains, yet smallholder participation remains limited, and certification is often driven more by market pressures than environmental objectives. This study evaluates the environmental sustainability of RSPO-certified and non-certified smallholders in Surat Thani Province, Thailand. Results show that certified farmers achieve marginally higher overall sustainability scores, with significant improvement only in soil fertility management through mandatory soil and leaf analyses and frond mulching. These practices are supported by better training access and stronger social networks. No significant differences were observed in water management or agro-biodiversity conservation, which depend mainly on agroecological conditions. The findings suggest that RSPO certification alone does not ensure environmental sustainability. Broader sustainability transitions are driven by market dynamics, government extension, and farmer learning networks. Policies should promote sector-wide sustainability by scaling successful RSPO soil fertility initiatives – public – private partnerships linking mills, universities, and local authorities – and supporting integrated management of soil, water, and biodiversity alongside improved planting material and irrigation access to advance Thailand’s sustainable oil palm transition.