In connection with ongoingstudies in the Orchidaceae for Flora of Thailand, Dendrochilum gracile, D. longifolium, D. simile and Sarcoglyphis flava are recorded as new for Thailand. Illustrations and morphological descriptions of the newly recorded species are provided based on the Thai collections. Furthermore, general notes on the genera Dendrochilum and Sarcoglyphis in a Thai context are provided, including keys to all species currently recognized for Thailand.