Check out the pic, showing O.J. singing a ton of memorabilia in a private room at a Las Vegas hotel Tuesday night, and he plans to do the same Wednesday night. We're told he was in the room for 2 hours signing a variety of items, including USC and Buffalo Bills helmets.

The gear will most likely be sold to auctioneers.

Now here's the rub. O.J. owes a whopping $100 MILLION to the Goldman and Brown families -- the original judgment was $33.5 mil, but 22 years of interest really adds up.

If Simpson makes money, it's subject to seizure to satisfy the judgment. The families have gotten almost nothing from Simpson in the 22 years, and O.J. has made it clear ... he has no interest in paying.

If he were to take money under the table to avoid paying the judgment, he would be violating federal tax laws. If he violates the law, his parole can be revoked and he can be thrown back in prison.

Cat ... meet mouse.