This species of monitor lizard appears to be rather uncommon, as sightings are quite rare. It occurs in a broad range of habitats including lowland swamps, stream gullies in hilly areas, and lower montane forest to around 1200 metres elevation. It has also been reported from mangrove habitat, which is also a typical haunt of the larger and more common water monitor.

The species is called rough-necked monitor due to the presence of enlarged nuchal scales (i.e. the scales on the back of the neck) which are strongly keeled. Other identifying features include the long, pointed, convex snout, the base of which is markedly concave.

The nostril lies midway between the tip of the snout and front of the eye (unlike the water monitor where the nostril is near the tip of the snout). The skull bears a strong ridge above the eye. The neck is relatively long, and the tail may be up to 1.6 times the snout-vent length.

The species is mainly dark grey throughout, with yellowish banding across the back and yellowish mottling on the neck and limbs. Juveniles are more strongly marked than adults.

This lizard may be encountered on the forest floor, near streams, on fallen logs or on tree trunks. Typically it takes shelter inside tree holes. Little is known of its feeding ecology, though crabs appear to be part of its diet in habitats where there are sufficient crabs.

The rough-necked monitor occurs in southern Burma, southern Thailand, Peninsular Malaysia (including the southernmost state of Johor), Sumatra and Borneo. There are no records, historical or recent, from Singapore.