The Krabi mouth-brooding betta, Betta simplex, is a species of gourami endemic to Krabi Province, Thailand. It inhabits karst springs and wetlands, where it lives amongst vegetation close to the banks. This species can reach a length of 8 cm (3 in). This species can also be found in the aquarium trade and is taken from the wild for this purpose. The International Union for Conservation of Nature has assessed it as being "critically endangered" due to over-exploitation and the degradation of its restricted habitat by pollution and development of the surrounding land for farming.