This analysis examines agricultural investment in the Mekong region, focusing on Cambodia, Laos, and Vietnam, to promote Responsible Agricultural Investment (RAI). It highlights the transition from large agricultural concessions to contract farming since the 1980s and the current efforts to develop supportive policies, such as Cambodia’s Contract Farming Law, Laos’ guidelines on contract farming, and Vietnam’s revised Land Law. Using a comparative framework, the study evaluates factors like investment models, government roles, and contract terms, alongside outcomes such as land tenure security and environmental impacts. Six case studies illustrate diverse contract farming models across crops like rubber, cassava, tea, sugarcane, and rice. The findings emphasize the need for clear contracts, enforceable terms, equitable benefits, and supportive policies that address local contexts and gender equity while strengthening farmer participation through cooperatives and secure land tenure mechanisms.