Previously, the species was classified as Microhyla berdmorei. Trofimets et al. (2024) revised the taxonomy and distinguished populations from Borneo, Sumatra, and Peninsular Malaysia as separate from the nominal M. berdmorei.

Microhyla sundaica is a small frog (maximum females reaching 31.4 mm; males approximately 3 mm shorter) that inhabits the forest floor. Its coloration consists of various shades of brown. Note the conspicuous markings across the shoulders and between the eyes. The dorsal skin is shagreened. The first finger is longer than half the length of the second finger. The fingers have well-developed adhesive discs with a medial groove. These discs are even wider and more clearly grooved at the toe tips, forming a pair of scale-like pads per toe. When gently stretched forward, the tibiotarsal articulation of the hind limb extends far beyond the snout tip. The toes are fully webbed.

In males, the throat and chin are dark, whereas in females they are beige. The belly and underside of the thighs are brightly yellow. The hind limbs feature 2–3 dark crossbars. The iris is uniformly grayish-bronze. Despite its small size, this species has long legs and can make impressive jumps.

Microhyla sundaica is mainly found in lowland primary and secondary rainforests but has been recorded at elevations of at least 1000 m a.s.l. We have never encountered this species in abundance at any site, which may be due to timing, location, or the species' secretive behavior—adults may only emerge under certain conditions. Trofimets et al. (2024) compiled natural history data from the literature. A recurring observation is that this species is most often encountered at temporarily flooded, shallow forest pools with abundant leaf litter.

Details of its reproductive biology and larval stages have been described by Leong (2004) for populations in Peninsular Malaysia. Tadpoles are suspension feeders in the mid-water column, lacking keratinized mouthparts. The spiracle is positioned medially on the belly. Tadpoles are delicately built and reach a maximum total length of 23 mm.