Although this species of sticky frog likely does not burrow itself, it has been found sitting at the entrances of burrows, which inspired its name (Inger 1966). Kalophrynus subterrestris is reportedly found in lowland primary and good secondary forests of Brunei, Sabah, Sarawak, and north-central Kalimantan; however, modern evidence from these regions—including DNA data and well-documented photographs of living specimens—is currently lacking.

It is a small species among sticky frogs, measuring only 21–23 mm snout–vent length (SVL) in males and 26–27 mm in females. The outermost finger (IV) and outermost toe (V) are very short, with finger IV shorter than the terminal segment of finger III. There is only one tubercle beneath the fourth finger (compared to two in, for example, K. punctatus). Two metatarsal tubercles are present but low.

A light stripe on the snout is absent, and usually there is no light stripe on the sides of the body or only a very fine line. The thighs lack clearly defined lines, banding, or ocelli. The dorsal skin is coarsely granular. There is no gland or fold behind the eardrum. The dorsal coloration has been reported as black or dark gray, while the sides of the body are lighter in tone. Inger (1966) reported relatively large ova (1.8–2.0 mm), which might suggest endotrophic larvae, as has been reported in other Kalophrynus species.