You should make the thesis statement more interesting. It should be "arguable." That means some people would disagree with it. Isn't that a funny requirement? But it makes sense because if you say something no one would disagree with, it is not worth writing about.
So... do something like this:
Being bilingual is even more advantageous than being wealthy. ---This is something people might disagree with, and that is what makes it interesting.
So how should you write the intro paragraph? You should write some sentence that are interesting enough to make the reader start thinking about why bilingualism is advantageous. :-)