This study is aimed to clarify species composition and distribution of benthic dinoflagellate from Thailand as well as their toxicities using morphological observation, phylogenetic analyses and mouse bioassay. Furthermore, we also determine the effects of environmental factors such as temperature and salinity on benthic dinoflagellate from Thailand in order to know the relative importance of these factors on their growth and to use these observation for the risk assessment of toxic dinoflagellate bloom events in Thailand.