Despite substantial land cover changes and a history of recurrent droughts, the Bila watershed has not been subjected to comprehensive spatial drought vulnerability. This study overcomes this research gap by integrating a geographic information system (GIS) with the frequency ratio (FR) method to produce an accurate and scientifically based map of drought-prone zones. To the best of the authors’ knowledge, this study is the first to apply the frequency ratio (FR) method to assess drought vulnerability at the watershed scale in South Sulawesi, thus contributing a new and data-driven framework to advance spatial drought analysis in the tropical environment. The FR analysis used seven drought-related factors: rainfall, land cover, building density, hotspots, vegetation density, slope, and river distance. The results of the LST analysis revealed that approximately 43.25% of the area in the Bila watershed experienced drought, primarily due to moderate building density and residential land cover, as indicated by high FR values of 2.98 and 2.89, respectively. The results of mapping the Bila watershed's drought-prone zones show that areas with high to very high drought vulnerability categories tend to be concentrated in paddy fields, residential, dryland agriculture, and areas with moderate building density. The spatial distribution pattern reveals that the downstream areas of the Bila watershed exhibit a greater level of drought vulnerability than the upstream regions do.