The Louisiana rapper pled guilty to misdemeanor possession of marijuana. In exchange, prosecutors dropped charges of possession of a controlled substance and failure to maintain lane ... this according to docs from the Coweta County D.A.'s Office.

It's a sweet deal for Boosie, who gets 6 months probation and a $1,000 fine ... but no time behind bars. The judge has already signed off on the deal.

It could have been a lot more serious. As we reported. Boosie was busted last April after cops pulled him over in his Dodge Charger for swerving lanes and almost hitting another car. During the stop, cops found weed, a gun and more than $20k in cash.

Boosie was never booked for the gun -- it's likely he was licensed to have it.

He'd previously served 5 years in Louisiana for drug charges, and could have been hit with a year in a Georgia jail if convicted on all charges.