Master P -- FLASH MOB DISASTER ... Rapper Storms Out of Surprise Birthday Party

Master P hates flash mobs ... HATES THEM ... at least, it seemed that way when he stormed away from a mob that was organized especially for his birthday yesterday ... and TMZ got the whole thing on tape.

P was enjoying a nice relaxing lunch with his son Romeo in Santa Monica ... when a flash mob broke out right in front of Master P's table.

But Mr. P clearly wasn't amused ... and right in the middle of the performance (during a Gangnam Style routine), the No Limit founder got out of his seat and beelined it for the exit, clearly upset.

As he left the restaurant, a woman connected to the event chased after P and begged him to come back ... saying, "Don't leave ... it's your birthday."

The woman also told P the name of the person who organized the event in the hopes P would have a change of heart ... but P didn't care, and continued to storm off.

On his way out, we commented to P, "That didn't go like they planned, huh?"

His response -- "Nah, it did not."

So, why was P so pissed off? We're trying to find out ... maybe he just isn't a fan of Psy?