The Situation -- Another HUGE Contract for Tanning Beds

The Situation is getting even richer ... now that he 's locked down ANOTHER 6-figure check to be the face of a new tanning salon business ... TMZ has learned.

Sources involved in the deal tell us ... Sitch just signed a 6-figure contract with the Boca Tanning Club. We're told The Situation's deal was pretty sweet -- because along with the FAT paycheck, the company he runs with his brother -- MPS Entertainment -- also got an ownership stake in the business.

We're told Sitch wants to open FOUR new salons in Jersey within the next year -- and he's already recruiting friends and family members to work in the shops.