An agent-based model (ABM) was co-designed with a group of rainfedlowland rice farmers from a village in Northeast Thailand to investigate the interactions between wateravailability and labour migration in rice production. A preliminary agrarian system analysis of the study site (LamDome Yai watershed in Southern Ubon Ratchathani Province) suggested to define three main types of farminghouseholds according to their agro-ecological constraints and opportunities, farming practices, and socioeconomicstrategies. To reflect this typology, a group of 11 farming households were selected. The wives andhusbands of each household were involved in the co-design of the conceptual ABM through a series of fieldworkshops based on role-playing games (15-18 participants). To specify the rule-based algorithms related to ricecropping activities, a smaller group (6-10 participants) engaged in the design of UML activity diagrams.Implemented with the Cormas platform, the corresponding computer simulation model was introduced to theparticipating farmers. Showcasing the "business-as-usual" scenario enabled to fine tune the calibration and themeans of observation. The participants were then requested to suggest scenarios of interest to them to beexplored with the model. In this 4-year long process, the successive use of role-playing games, UML activitydiagrams and computer simulations with the participating farmers accounted for about two-thirds of the varioussources of information (as a complement to the one-third represented by farm surveys and secondary data) usedto specify the model. It resulted in increasing the sense of ownership of the model by the farmers. At completionof the process, a special seminar was organized at the regional Faculty of Agriculture of Ubon RatchathaniUniversity during which four collaborative farmers presented and discussed at length "their" model in front ofseventy graduate students and faculty staff.