Ray Allen -- DROPS $10K PER HAND ... In High Stakes Vegas Blackjack

Ray Allen was LIGHTING UP a blackjack table in Vegas over the weekend ... dropping $10k per hand at the Bellagio ... and TMZ Sports has the pics.

The Miami Heat superstar decided to try his luck with the cards on Saturday night ... and posted up at a $1,000 minimum table in the exclusive Club Prive high-rollers lounge.

You can check out his stack (don't worry, it's OK to look) ... it appears Ray was gambling with somewhere between 30 and 40 yellow chips ($1,000-a-pop).

Our casino sources who were there during the gambling run tell us Ray -- who once signed an $80 MILLION contract -- didn't have a great showing at the table ... and walked away empty handed.

Hopefully, he stayed long enough to get his free drink.

We reached out to Ray's camp for comment -- so far, no word back ... but you know somewhere, Charles Barkley is smilin'.