In the remote highland forest-farmland ecosystem of Doi Tiew, a Hmong village in Tha Wang Pha District of Nan province, Northern Thailand a land use conflict is taking place between the local herders and two government agencies (Nanthaburi National Park and the Nam Khang headwater research and development unit) having different interests, objectives and perceptions on land use and land management. In this research we are using the integrative companion modeling approach (http://www.commod.org) to co-construct a simulation tool representing the dynamic interactions between vegetation dynamics, reforestation efforts, and livestock grazing at the study site. This paper focus on the participatory modeling process implemented with concerned stakeholders. Three main investigation tools were used to gather knowledge on the relevant ecological and human decision making processes: field surveys (history of land use and analysis of vegetation dynamics at landscape level), farmers' interviews (analysis of decision making and determining factors across different types of farms), institutional analysis (changes in land use policy and related state interventions). This knowledge was first assembled in simple gaming exercises used with local herders and foresters to validate the researchers' understanding of key interactions regulating vegetation and land use dynamics. The outputs of these collaborative modeling activities were used to design the suitable features and rules of a role-playing game representing the complex human and ecological interactions at the landscape level. This game allowed stakeholders to criticize and improve this comprehensive formalization of the landscape dynamics. It was also used to introduce gaming and simulation exercises and to stimulate stakeholders to identify possible future land management scenarios mitigating the current conflict. The results from two gaming and simulation field workshops allowed local stakeholders to set up of co-management ac