Well, your thesis statement involves your reasons as to why cigarettes should be illegal. For example your thesis statement could be cigarettes should be illegal because they can cause lung cancer, they can make it difficult for blood to move around the body, and you can become addicted to them. Your three reasons being you can get lung cancer, they can make it more difficult for blood to pump through your body, and you can become addicted. And if you’re arguing for cigarettes being illegal, then definitely start the thesis statement with “cigarettes should be illegal because” and then tack on your reasons why.