Snakes use venom for eating, it's not a weapon. Venom is actually modified saliva. Being such, part of the problem with a snake bite is tissue damage due to the prey (or you) starting to be predigested.
It is NOT in the snake's interest to inject you with venom. The snake is extremely vulnerable while it is without venom and it uses a lot of energy for the snake to reproduce the venom. That's why the vast majority of bites a 'dry' bites (no venom). That's why 8,000 people can be bitten and only around 30 die in Thailand.
|Photo by Benjamin Schaye|
The green vipers tend to hang out in similarly color foliage. It's difficult to see them. If you pay attention to where you put your hands, which bushes you walk closely to, and exercise some common sense, you should never have to deal with a snake bite.