Two species of coastal Canavalia Adans. (Fabaceae, Papilionoideae, Diocleae), C.cathartica Thouars and C. rosea (Sw.) DC. are found in Thailand.Morphological, distribution, and ecological studies were done to clarify the confusion between the species. Taxonomic notes and utilization are presented. A key to the species based on habit, leaflet, and seed characteristics is provided. In brief, C. cathartica is a twining species, has acute to acuminate leaflet apex, and longer hilum, occupying ≥60% of the seed length, while C. rosea, a prostrate vine, has more rounded to retuse leaflet apex, and shorter hilum, covering normally <60% of the seed length. Both species are distributed in the coastal areas, in the South-Western, Central, South-Eastern and Peninsular Thailand, and often occur in the same localities. However, C. cathartica can be found more inland, in moist areas or near the water resources.