The article highlights the role of partisan ethnography in studying the chains of co-optation of grassroots environmental activism in ecologically and politically sensitive contexts. In Thailand, such chains are often undergoing the process of institutionalization of eco-Buddhist approaches to nature conservation, also concurring with the detachment of grassroots socio-environmental activism from the recent, urban based pro-democracy uprisings. The discussion will focus on the recent history of the eco-politics related to natural resources conservation in the Nan River Basin (Northern Thailand). It will describe how, since the 1980s, eco-Buddhist NGOs, Royal think tanks, international cooperation organizations, and corporate C.S.E.R. programs, which comply with the latter agencies, have systematically tended to manipulate pioneer, grassroots eco-political imagination and the organisational know-how of local environmental activists. These powerful institutional actors demonstrated interest in the Buddhist moralization of local ecological beliefs and praxis as a strategy to afford privileges of access to land, water, and forest resources through forms of internal “green grabbing”. At stake here is the fact that, beyond the grabbing of Thai river basins’ contested landscapes, activists’ radical imaginations and alter-political practices – an intangible component of such landscapes - are subject to a form of intellectual and political grabbing. The anthropological enterprise and the ethnographic encounter, conceived as partisan collaboration, nevertheless show that forms of patient resistance to such structural dynamics of co-optation might also express an unexpected source for the creative rearticulation of dissent and alter-political imaginations.