Rihanna to Chris Brown — How Could You Leave My Ass?

0522_rihanna_instagramRihanna just gave ex-boyfriend Chris Brown a little taste of what he”s missing … her perfectly sculpted ass.

RiRi just posted an extreme close-up shot of her nearly bare derriere in shorts that are so tiny, her THONG is hanging out of “em.

Rihanna added a caption saying the pic was from the set of her new music video … but we think it”s pretty obvious the photo was for an audience of 1 — Chris … who was recently spotted out with his other sometimes-GF Karrueche Tran (who definitely doesn”t have an ass like Ri). 

Think he”s regretting the breakup yet