Universities are places that vigorously contribute to the UN Sustainable Development Goals (SDGs). The green university concept that reflects the fundamental principles of the university on environment and sustainability has become well-established among universities’ campus planning and design worldwide. The UI GreenMetric World University Rankings is one of the green university indexes that aims to measure campus sustainability efforts. This study focuses on an indicator calculating the total area on campus covered by forest vegetation because it is a crucial landscape component that provides ecosystem services and environmental benefits for Kasetsart University (KU). However, the practical methodology to assess areas covered in vegetation in the form of forest was unavailable. Therefore, we applied definitions of the forest from 1) Global Forest Resources Assessments (FRA) of the Food and Agriculture Organization (FAO) and 2) the United Nations Framework Convention on Climate Change (UNFCCC) to the campus context, an area of 10x10 m, over 10% of which was covered by a canopy of trees at least 5 m in height was considered to be a forest area. Campus tree datasets – tree height, average tree canopy width, and location – were used for spatial analysis in ArcGIS. The results revealed a variation of results from 3 analysis methods. The study using Monte Carlo Simulation on a 10x10 m grid layer map revealed that 24.44 ha of the total campus area of 140.51 ha was covered in vegetation in the form of forest (17.39%). The Monte Carlo Simulation increases the validity of the forest area assessment. Groups of large trees located on the campus provide ecosystem services. Therefore, it is recommended that these urban forests be conserved as living labs to benefit the university campus’s stakeholders and Bangkok’s residents.