Following a historical outline, the methods and results of a taxonomic revision of Liparis in Thailand are presented. Applying the traditional methods and techniques of morphology-based botanical revision work, the revision mainly relied on examination of dried and liquid-preserved specimens from 13 herbaria. However, the herbarium studies were supplemented with observations of live plants made during 24 field trips to five of the seven floristic regions of Thailand. The taxonomic value of selected morphological characters is assessed, and ecological aspects are surveyed together with occurrence patterns in Thailand and the overall geographic affinities of the Liparis species represented in the Thai flora. Thirty-seven species are accepted, whereas reports of L. distans and L. kwangtungensis from Thailand are treated as dubious. One new species, L. buddhawongii, is described as new, based on material from Doi Ang Khang in Chiang Mai province. Full taxonomic accounts are provided for the genus and species, including a dichotomous key to the species. Whereas the synonymies are intended to be complete, all morphological descriptions have been prepared exclusively from Thai material. The accepted names L. balansae and L. resupinata are lectotypified, whereas a neotype is designated for L. ferruginea; L. downii and L. melanoglossa are proposed as new taxonomic (heterotypic) synonyms. All accepted species are illustrated by line drawings, and references are provided to additional good illustrations in the literature.