I want my boyfriend to wear a thong but how do i ask?

I’m into all sorts of undies and my bf (m19)and i (m19) are not super freaky. I have worn jocks infront of him but never more then that. Everytime i wear briefs or anything infront of him he gives me a wedgie which in turns give me a thong. He has commented how he likes o feel dominated but i really really want to see him in one but i don’t think he would feel comfortable or manly in it. How did i ask?