Betta mahachaiensis

Known only from a handful of localities in Bangkok, Samut Sakhon, Samut Songkhram and Samut Prakan provinces in central Thailand, all of which lie on the coast of the Gulf of Thailand.

Most habitats are in close proximity to Bangkok, which continues to expand rapidly, are considered under extreme threat, and recent surveys have failed to confirm that the fish is still present in Samut Songkhram and Samut Prakan.