It is endemic to the Mekong River Basin in southeast Asia, where it is found in ditches, canals and ponds.

The maximum recorded length of Oryzias mekongensis as an unsexed male is about 3 centimeters or about 1.18 inches.

It is mainly found in water that has a lot of growth of submerged aquatic plants with divided leaves.

[3] The major threats to this species' population rate would include habitat destruction and degradation that is primarily caused by urban development and also agriculture.

[1] The distribution of the Oryzias mekongensis includes the following areas: Uwa, Hiroshi; Magtoon, Wichian (May 9, 1986).