Feminism has gotten to be a very broad subject in recent years. It used to be that "feminism" was understood to focus on women's right to vote and to own their own property. But feminism has now become so involved with so many different human affairs that it would seem like an impossible task to discuss the movement in a single article or even a book. Therefore, I would suggest that you could find a thesis statement more easily if you would limit your intended discussion to a single aspect of feminism.
Wikipedia contains a lot of interesting information about Feminism (see reference link below). An aspect of the subject that seems fairly fresh is "post feminism." According to Wikipedia:
The term post-feminism is used to describe a range of viewpoints reacting to feminism since the 1980s. While not being "anti-feminist", post-feminists believe that women have achieved second wave goals while being critical of third wave feminist goals.
I suggest that you do a little reading up on the subject before trying to formulate a thesis statement. You ought to be able to find material for several good thesis statements in the Wikipedia article. Of course, your statement should be based on what you personally believe. But I feel sure you would find it easier to take a stand on a single aspect of feminism than on the centuries-old, endlessly debated subject as a whole.