More than 100 lichens have been found and identified in Thailand over the last century. Lichens perform useful environmental functions. Normally, they grow on trees, rocks and soils, in various forms and colours. They provide shelter and food for animals and plants. Lichens can also be used as indicators of air pollution, and some are researched for drugs, dyes, deodorants and extracts. This paper presents an ontology for lichens in Thailand, using lichen data from Khao Pluang, in Lopburi, Thailand. The database developed makes major contributions in the amount of knowledge on lichens that it stores, including the latitude and longitude of lichens at Khao Pluang specifically, and images of lichens. The system was implemented via web and mobile applications. The ontology knowledge consists of 6 main classes: 1) scientific name, 2) lichen type, 3) date found, 4) uses of the lichen, 5) function as an air pollution indicator, and 6) specific features of the individual lichen. Evaluation of the system was carried out by lichen and ontology specialists using the Software Usability Measurement Inventory (SUMI).