Ray J's Shaving Gel Ad -- I'm a Professional Fighter ... of Ingrown Hairs

The death of Whitney Houston hasn't diminished the marketing value of her ex-boyfriend Ray J -- TMZ has learned the singer just inked a major deal ... to fight the war on ingrown hairs.

Ray J is officially the new face of Prince Reigns shaving serum ... and according to the singer's rep, the deal is worth up to $1 million bucks ... though the rep wouldn't divulge the exact terms of the contract.

A rep for the company tells us Sophie Monk signed a similar deal.

Fun Fact -- Ray's former sex tape partner Kim Kardashian has also dabbled in the body hair removal business -- inking a deal of her own with the TRIA laser hair removal system a few years ago.