The freshwater Calanoida (Crustacea: Copepoda) of Thailand

14 Species of freshwater Calanoida in Thailand are reported in this study. The most common species is Neodiaptomus botulifer. Most of these belong to the Southeast Asian species, the remainder are either Indian or East Asian copepods. The zoogeographical demarcation of copepods in Thailand is not very distinct due to its interconnecting riverine and reservoir systems as well as frequent flood. The peculiarity of the Thai Calanoida and their distribution is discussed in a Southeast Asia context. A taxonomic key to the Thai Calanoida is formulated.