The keeled rat snake occurs in a variety of lowland habitats, but appears more common in secondary forest and sparsely wooded, agricultural areas. It is less common in primary forest, seeming to prefer forest-edge habitats.

This is by far the largest of the rat snakes of the Ptyas genus, reaching an impressive 4 metres total length. From a distance this snake could easily be confused with the king cobra Ophiophagus hannah.

The body is of moderate thickness, somewhat triangular in cross-section, and the head is wider than the body. The eyes are very large.

The front part of the body is dark brownish grey, sometimes with faint pale barring, the middle part is black and cream in a distinctive chequered pattern, and the posterior part is predominantly cream with scattered black-edged scales. The tail is mainly black with scattered pale spots, and the throat is white or cream, grading to dark grey on the belly.

Its diet comprises a variety of rodents and large frogs, hence its occurrence in agricultural areas.

This impressive rat snake ranges from southern China through Burma, Thailand, Vietnam, Peninsular Malaysia and Singapore to Sumatra, Java, Borneo and the Philippines.