Monitoring and mapping land use and land cover (LULC) changes is crucial for determining plausible resource availability in the future, and for providing policy implications towards the landscape's sustainable management. The LULC changes brought by economic land concessions and high deforestation are common issues in Koah Nheaek of the Mondulkiri province, distressing the sustainability of linked natural resources and agroecosystems. Determining its landscape's occurred changes and projection are vital inputs to succeeding policy programs as Koah Nheaek implements the Rectangle 4 (i.e., inclusive and sustainable development) of the Rectangular Strategy Phase IV (2018-2023). In this study, the LULC changes (2000-2020) in Koah Nheaek were analyzed using Google Earth Engine (i.e., the random forest). Corresponding to the LULC dynamics concept, forest had the highest loss (37% change) while wood shrub, grassland, orchard, and agriculture land gained a significant increase. In addition to the loss during the last 20 years, the forest was again degraded about 16% based on the 2030 projection using Markov-CA model. On the other hand, using General Linear Method, the trajectories and projection were supported by the inputs from focus group discussion of stakeholders. For this regression analysis, significant factors influencing decisions for current and future agricultural expansion included the household size and the inheritable parcel size. Upon this biophysical and social evidence, the Rectangle 4 implementation is recommended to be strictly enhanced to achieve its goals. This study suggests sustainable land measures (Good Agricultural Practices, Climate Smart Agriculture, Comprehensive Land Use Planning, and Agroforestry) to balance and manage land uses as a key to sustainability.