How do I thin out my thick hair?

I'm asian and i have straight hair, but the problem is that its is really thick. Like if i dont gel it it gets all poofy. How do I make it so that my hair will actually go down be more bouncy?? My hair is about 3-4 inches long and its still wont go down unless I wet it but when it dries up it poofs up again. I want to make my grow my hair long but I afraid that it's thickness will make it look weird. Are there any hair products that will thin it out?? I go to the barber for thinning shears but my hair gets poofy in about 2 weeks.