The low-lying areas in Walatung Village, Pandawan Subdistrict, Hulu Sungai Tengah Regency have great potential for rice cultivation but are hampered by soil acidity, seasonal flooding, and high biophysical variability. This study aims to analyze the biophysical conditions of the land, evaluate its suitability for swamp rice (Oryza sativa) using a fuzzy set–GIS approach compared to the conventional FAO method, and develop a Fuzzy Logic-Based Soil Quality Index as a basis for land optimization. The analysis was conducted at five sampling points representing shallow, medium, and deep wetland typologies, using soil data (texture, pH, organic carbon, total nitrogen, C/N ratio, cation exchange capacity), SRTM DEM, Topographic Wetness Index (TWI), CHIRPS precipitation data (2016–2025), and historical flooding data obtained from farmer interviews. The results indicate that soil pH (4.34–5.53) and duration of waterlogging are the dominant limiting factors across the entire region. The FAO evaluation resulted in S2 class covering 13%, S3 80%, and N 7%, while the fuzzy-GIS method produced a continuous LSI of 0.140–0.587 with 100% class consistency with the FAO; the S1 class was not found due to systemic soil acidity. The Soil Quality Index ranged from 0.57 to 0.78; organic carbon was not a limiting factor, but its high values (10.61–14.10%) in deep peatlands indicate the potential for peatland. Zone-based optimization strategies are recommended, namely nitrogen fertilization in shallow peatlands, dolomite liming and channel normalization in intermediate peatlands, and gradual reclamation or wetland conservation in deep peatlands. The fuzzy-GIS approach has proven to complement the FAO method with more detailed spatial representation and the ability to capture gradual transitions in land conditions.