Background: Upper Songkhla Lake, a single lagoon of Thailand, is surrounded by sandy, mangrove, and swamp forests. Many plants growing in these areas have medicinal properties, however they have never been investigated. The aim of this study was to explore medicinal plants from upper Songkhla Lake, Songkhla and Phatthalung provinces. Materials and Methods: Semi-structured interviews were conducted with seven key informants to get information regarding the local names, parts and utilization, method of preparation, route of administration and properties of plants. Voucher specimens were prepared, identified and deposited. Results: In total, 95 species belonging to 82 genera in 46 families were found. Among them 26 groups of ailments could be classified, and most of the herbal plants were used for antipyretic (24.30%). Conclusion: It was found that the natural sources of medicinal plants were damaged by many human activities. Therefore, this compilation of medicinal plants will be the data evidence for further conservation of the plants.