UB40 Singer Ali Campbell -- Red Wine and Nipple Rings!

Former UB40 singer Ali Campbell let it all hang out in New Zealand this weekend ... by going topless in public.

While holding a glass of what appeared to be red red wine, the 53-year-old flashed his buxom man breasts on a balcony in Auckland.

FYI -- UB40 released "Red Red Wine" back in 1983. Unclear if he was still rockin' the nipple ring back then.