Currently, in Thailand, proposed development projects require an Environmental Impact Assessment (EIA) as part of the approval process. Effective public participation in the process of developing an EIA helps to ensure fairness and equity for the EIA system. It enables stakeholders to share information and exchange views concerning the complex issues and likely impacts of the proposed development project. Thailand has substantial legislation and regulations that aim to enable public participation for EIA processes. However, implementation of public participation provisions is failing at least to some degree. This article explores how the law concerning public participation might be improved to enable better implementation of the EIA system in Thailand. Some methods for employing effective public participation to support the implementation of EIAs are proposed.