Thailand has announced ambitious plans to reduce greenhouse gas emissions, including a programme that allows private companies to earn carbon credits from protecting and restoring mangroves. In 2023, the Department of Marine and Coastal Resources (DMCR) began enrolling local communities and private firms in this scheme. We examine whether communities can participate fairly, drawing on 18 semi-structured interviews with government officials, NGOs, community leaders and private sector actors. We identify five barriers: unclear policies that leave communities uncertain about their rights; benefit-sharing arrangements widely perceived as unfair; divergent views among communities and NGOs about carbon offsetting; knowledge and capacity gaps that limit meaningful engagement; and prohibitive verification and implementation costs. We argue that these barriers are not discrete problems but mutually reinforcing features of T-VER's governance architecture, producing distributive, procedural and recognitional injustices that constrain participation. State mediation does not necessarily protect communities. Without formal rights, independent accountability mechanisms and accessible verification pathways, it can instead concentrate power in the hands of state and corporate actors. Thailand's experience raises important concerns for other countries where forest land remains under state control. We conclude with recommendations for reform that could make community participation more equitable and projects more durable.