I don't smoke, so smokers feel free to call me a biggot for this, but I think it's common sense that smoking around ANY animal is a bad idea.
I see it as potentially harmful in two ways: inhalation, and burns.
The tobacco itself MIGHT not have much affect on them. However smoke is probably irritating, and it's the additives in cigarettes that I would be most concerned about; those will likely harm nearly any form of life as we know it.
If the person is handling the snake (or tending to it's care) while smoking, there's an obvious risk that the snake could get burned.