Ray J Hits $17k Jackpot Playing Penny Slots at Casino

Ray J's living proof the rich just get richer ... because his investment yielded a 17,000 percent return on his investment ... yes, 17,000 PERCENT!!!

Ray J was playing a penny-slot game called "Buffalo" and won $17,000. We're told he plunked down a total of $100 so, yeah, it was a good day at the slots.

In case you want in ... Ray hit up the San Manuel Casino in San Bernardino County. It was quite the scene ... a crowd gathered to watch Ray J rake in the dough.

He played the slots because he considers himself an old man now, and that's what old folks do. BTW ... he's 40.

Ray has retired his days as a big gambler on table games, particularly roulette ... and his most recent lucky streak is probably a sign that's a good idea.

It's not like he needs money ... Ray's Raycon earbuds hit a milestone earlier this year ... 1 million unique customers who paid between $80 and $150 a pop. Translation ... he made a fortune, and that's just on one product.