"leptomantis belalongensis" is endemic to the temburong district of brunei. it occurs only in several small tributaries of the sungai temburong and sungai belalong rivers, in the area of their confluence. the frog's specific name refers to the latter river; the latin suffix "-ensis" means "originating in". its closest relatives include "rhacophorus bimaculatus", "rhacophorus catamitus", "rhacophorus gadingensis", and "rhacophorus gauni".