Background. Thysanote Krøyer, 1863 (Copepoda, Siphonostomatoida, Lernaeopodidae) comprises 19 species of marine parasite that infect fishes. This report establishes a new Thysanote species based on new collections of copepods. The taxonomic status of this genus is not fully understood and therefore more relevant contributions are needed. Materials and Methods. The species description is based on male and female specimens collected from the olfactory sacs of spotted scat, Scatophagus argus, captured off Thailand in 2003. The specimens were studied using standard light and scanning electron microscopy techniques. Results. The studied specimens were assigned to Thysanote based on the presence of maxillary- and posterior processes and they exhibited unique characteristics such as distinctly short length of their maxillary- and posterior processes. Conclusion. Based on their unique characteristics, a new Thysanote species is erected, and named Thysanote chalermwati n. sp., thus bringing the number of congeners to 20.