Kenneth Petty was put on home detention for up to 120 days -- and all because he threatened Offset on social media.

According to court docs, obtained by TMZ, Petty violated his federal probation by "making threatening remarks while in the company of someone with a criminal record."

A judge ordered Petty to be placed on house arrest for as long as 4 months to keep a close eye on his activities. As part of being monitored, Petty might have to be fitted with an electronic GPS ankle bracelet, although that hasn't been determined yet.

Petty's new troubles began last week when he posted an Instagram video, featuring himself and two buddies sounding off on Cardi B's husband. The trio was standing across the street from an NYC hotel where Offset was supposedly staying -- and they were all acting pretty menacing.

In response, Offset later posted his own video on social media, showing himself chuckling on the tarmac outside his private jet -- which was nowhere near the hotel.

Clearly, the feds didn't find it funny ... because they wasted no time putting a stop to it -- and Petty!!

Over the years, Petty has been convicted of attempted rape and attempted murder and has served two stints in prison. In 2022, he was sentenced to 3 years probation after he failed to register as a sex offender in California.