the thesis statement is supposed to be the main idea of your whole paper. if you were trying to convince people that we should legalize marijuana in your paper then an example would be "legalization of marijuana in the us would reduce crime and form a more productive society through its positive uses."
I have problems with those too! :( I usually start mine off with "While. . . , this also happened". In the "this Ali happened" add in whatever your essay is going to be about. I hope this helps, and good luck!