Lil Scrappy LOCKED UP ... After Refusing Urine Test!! (Mugshot) -- Details Inside

Lil Scrappy is a lil' jailbird -- the rapper-slash-reality star turned himself in to an ATL jail this morning after cops say he refused to submit to a court-ordered urine test ... TMZ has learned. We broke the story ... officials say Scrappy violated his probation back in March after a dispute over a pee test.

According to court officials, Scrappy tried to turn in a urine sample that was cold to the touch and may have been tampered with ... and when asked to submit another cup, he refused. The court eventually issued a warrant for his arrest ... and moments ago, the "Love & Hip Hop: Atlanta" star turned himself in.

Lil Scrappy 'Love and Hip Hop' Check Garnished To Help Pay Off a $100,000 Debt!! The Court Signed Off On It!! -- Details Inside

Lil Scrappy 'Love and Hip Hop' Check Garnished To Help Pay Off a $100,000 Debt!! SMH -- "Love & Hip Hop" star Lil Scrappy better have some "Money in the Bank" left over from his rap career ... because his TV checks are about to be garnished ... to help pay off a $100,000 debt.

Long story short ... Scrappy was supposed to cough up $72,218.68 to a concert booking company called Heavy Rotation back in 2010 -- after he lost a legal battle in GA court. But according to HR, Scrappy never paid up.

The debt has since ballooned to $108,510.38 with interest and attorney's fees. Tired of waiting for their loot ... HR requested to have chunks of Scrappy's "Love & Hip Hop" cash go straight to them first, until the debt's satisifed ... which the court signed off on. Might be time to focus on that music again.