What snakes are in Vietnam?

A common term used by GIs in the field was, "watch out for those two step vipers." Although not familar with the serpent, the understanding was, once it bit you, you could only take two more steps before you dropped (from the poison).

Other than that, unfortunately for those that got shook up by the sudden gunfire, most GIs shot snakes on sight when moving thru the swamps and jungles.