While Offset's recovering from the shooting at Florida's Hard Rock Hotel and Casino, he's also catching heat over $100K he borrowed from a Detroit casino -- a debt he's trying to square away ... TMZ has learned.

The MotorCity Casino Hotel is suing the rapper, claiming he opened a credit line of $100K with the casino so he could keep a night of gambling fun going back in March 2024.

According to the docs, obtained by TMZ, the casino couldn't get in touch with Offset ... so, it tried to take the money out of his account directly -- as both parties agreed when he opened the credit line -- but, allegedly there wasn't enough money in it to pay off the debt.

The casino's suing Offset for breach of contract, fraud and more. A rep for Offset tells TMZ, "We are working toward a resolution."

The ex-Migos rapper's on a streak, a bad one, with casinos ... the lawsuit was filed just days before he was shot outside the Seminole Hard Rock Hotel and Casino in Florida.

TMZ broke the story ... he and Lil Tjay's crews got into a fight that ended with someone opening fire and hitting Offset in the leg. He was rushed to the hospital with non-life-threatening injuries. Lil Tjay was booked for disorderly conduct related to the fight ... he was released from jail the next day.

This is just the latest in a string of financial woes for Offset ... who had to pay the IRS more than $1.5 million in federal income tax after the department hit him with a lien.