The giant freshwater stingray (Himantura polylepis, also widely known by the junior synonym H. chaophraya) is a species of stingray in the family Dasyatidae.It is found in large rivers and estuaries in Indochina and Borneo, though historically it may have been more widely distributed in South and Southeast Asia.hese forces have resulted in substantial population declines in at least central Thailand and Cambodia. As a result, the International Union for Conservation of Nature (IUCN) has assessed the giant freshwater stingray as Endangered.