I know plenty of people who smoke and are definitely not losing weight. Don't smoke if you've already quit! Quitting is hard to do, and it's great that you were able to quit once, but starting again is a BAD idea, especially if you have asthma. Think about your pros and cons here:
PROS: *Maybe* smoking will help you lose weight (but it's no guarantee)
CONS: Smoking is not good for people who have asthma.
Smoking is not good for anyone.
Your lungs are gonna be so gross if you do it for a long time.
There are a lot of health problems associated with smoking.
There are probably more, but you get the point
The only way to lose weight is to exercise and eat healthy. Smoking is so not the way to go.