Two Malayan Pit Vipers. Both their bodies have a pattern of triangular markings, one on a light background, the other on a dark background. This is the only Asian pit viper with large crown scales and smooth dorsal scales.

Characteristically, on each side of its head, behind the eyes, it has a dark brown patch, bordered with a fine white line. The top of this patch is straight, the bottom is serrated.

Their snout is pointed and curved upward. This snake has long, hollow fangs that fold back against the roof of its mouth and which must be extended before it can bite.