The type locality of Philautus disgregus is the Danum Valley Field Center, Lahad Datu District, Sabah, and Sungai Pesu, Fourth Division, Sarawak, Malaysia (Borneo). As far as known, this is a lowland species occurring below 300 m elevation. The individuals shown in the accompanying photograph were recorded from Tawau Hills.

Males measure 21–23 mm in snout–vent length (SVL), and females 24–25 mm. The body of P. disgregus is stocky. The tympanum is distinct, and the nostrils are slightly raised. The canthus rostralis is distinct but not sharply defined. Elevated conical tubercles are present on the upper eyelid, and a curved supratympanic fold extends from the eye to the arm.The limbs are moderately long relative to SVL. All digits bear expanded adhesive discs. Finger webbing is reduced to the bases, while toe webbing is more developed. The outer metatarsal tubercle is absent, and the inner one is present and oval. The pupil is horizontally elliptical. The dorsal and lateral skin is relatively smooth but bears scattered low tubercles. The ventral surfaces of the head and trunk are coarsely granular. 

The lower eyelid is heavily pigmented. Dorsal coloration is brown or reddish brown, with a broad interorbital bar and a dark X-shaped marking on the back that extends onto the thighs. Two pale streaks run from the eyes to the upper lips. The throat, abdomen, and undersides of the limbs are densely mottled with brown. The iris is brown to reddish brown, lighter in the upper sector, or bronze with dark reticulation.

Virtually nothing is known about the biology of this species. Even casual observations, such as those on iNaturalist, remain scarce. Further research is clearly needed.