This study presents a methodology to determine suitable locations to establish energy facilities using para rubber trees (Hevea brasiliensis) as a biomass resource, with application in the southernmost provinces of Thailand. A Geographic Information System (GIS), along with the Analytic Hierarchy Process (AHP), were used to compute the influencing factors and constraints in consideration of environmental and socio-economic siting criteria. As the time scale of the analysis is over one life cycle of para rubber trees, the methodology is based on a secure supply of para rubberwood feedstock required to supply individual 9.5 MW biomass facilities for at least 20 years. This study found that the region of the southernmost provinces of Thailand has significant capacity to generate electricity using para rubber tree biomass. Out of 13,941 km2 of the study area, 4,890 km2 (35%) are either highly or moderately suitable to establish para rubberwood-based energy facilities. In conformity with the Very Small Power Producer (VSPP) policy of Thailand, and using para rubberwood biomass from trees at the end of their productive latex life-cycle, 12 power plants, with a total capacity of 114 MW, could be installed in the highly suitable areas, with an annual energy production of 767 GW h/yr and CO2e emission avoidances of 444 ktonnes, annually. When considering both the highly suitable and moderately suitable areas, 22 power plants, with a total capacity of 209 MW, could be installed, with an annual energy production of 1,406 GW h/yr and CO2e emission avoidances of 815 ktonnes, annually. This would correspond to nearly 7% of the current installed renewable power capacity of the generation portfolio of the Electricity Generating Authority of Thailand (EGAT). The results of the study show that para rubberwood fuel resources can make significant contributions in solving the energy issues of southern Thailand.