For graduate students, a thesis proposal is your opportunity to outline a problem and explain the significance of your work. A strong thesis statement should contain the following three elements:
Specific: You’re probably making multiple points within your dissertation, but your thesis should tie them all together into one specific research question. Your readers should understand the exact point you plan to make in your work.
Unique: A thesis statement should be unique and include some degree of controversy. You’re not trying to restate what everyone else is saying about that topic -- you’re most likely challenging a widely accepted view and inviting discussion and further research.
Succinct: A thesis statement should be as succinct as possible. You need to find a way to express your point in as few words as possible.