[2][3] The holotype, an adult male, measures 14 mm (0.6 in) in snout–vent length; females are unknown but presumably larger.

Dorsal colouration is brown with (male holotype) or without marbling (juvenile paratype).

The ventrum bears dark spots that form curvilinear, transverse rows on the throat.

[3] Phrynobatrachus taiensis is presumably a lowland rainforest species that, like its relatives, breeds in water.

If it is a forest-dependent species, then it is probably negatively affected by the loss of forest habitat caused by agricultural development, logging, and human settlements.