The victim -- who TMZ learned is a concert promoter named Kenneth -- tells us ... multiple attorneys have reached out to him to offer their services -- as in suing DaBaby.

Kenneth says he'll be going after the rapper and everyone involved in the brutal incident ... which he claims left him with cuts and bruises on his face.

As for what went down ... Kenneth says he was hired to put on a birthday party for rapper Stunna 4 Vegas at a Florida nightclub Thursday night and made a deal with DaBaby to host. He claims it was for a discounted rate of $30k because the rappers are friends.

Kenneth tells us he showed up with $20k and promised he could get DaBaby an additional $10k from his artist YC Woody ... but the rapper and his crew got pissed, and it quickly turned violent.

The promoter says he had to get checked out by a doctor because his injuries were so bad. He says video of the assault is difficult for him and his loved ones to watch. Kenneth also claims DaBaby's team made off with the $20k and hasn't returned it.

We broke the story ... DaBaby was initially detained and later arrested for battery in connection with the incident. According to the police report, Kenneth was robbed of $80, a credit card, an iPhone 7 and then doused with apple juice. It's certainly possible authorities will add a robbery charge.