"Thesis" typically refers to a doctoral dissertation and refers to the topic to be researched and analyzed. A thesis statement is typically for essay writing and the rules are:
1) One sentence: Statement of Fact + Opinion About that Fact (without using "I")
2) Typically found in the last sentence of the Introductory Paragraph
3) Used as a roadmap for the rest of your essay where everything you write supports (provides evidence) of your thesis statement.