Lil Tjay Claims Offset Made It Rain at Strip Club While Owing Him $10K

Lil Tjay is shedding some light on why he had beef with Offset before the Migos rapper got shot last month ... and as these things often start, it's over money.

Tjay dropped by "The Breakfast Club" on Wednesday ... and said at some point, he was at a casino with Offset -- and broke him off $10,000 because Offset was asking others to float him.

As Tjay tells it ... he later asked Offset when he would pay him back, and the rapper got "all tough" with him -- and then, more insultingly ... showered strippers with cash in front of Tjay.

Obviously, it's a pretty interesting story ... since, as we reported ... according to the FBI and the Seminole Police Department, Offset got into a brawl with a large group -- including Tjay, who was later arrested in relation to the fight -- outside the Seminole Hard Rock Hotel & Casino in Florida on the night of April 6.

Offset was shot in the melee -- and rushed to a local hospital, where he was treated and eventually released.

Tjay told 'TBC' hosts ... he doesn't really care about the money ... and he's over the beef with Offset.