Keith Sweat Is Begging Again...This Time To The Judge...

R&B singer Keith Sweat is singing the foreclosure blues ... because even after the bank took his house and sold it ... he's still on the hook for $250,000 -- this according to a new lawsuit.

PMI Mortgage filed the lawsuit against Sweat in Georgia -- claiming the singer defaulted on a $450,000 mortgage on his Detroit home, which he purchased in 2004.

Problem is -- the house was drowning underwater ... so when the bank sold it, it only recouped $200,000 ... a fraction of its losses.

PMI Mortgage sued Sweat for the balance -- $253,000 -- and since Keith failed to respond, a judge ruled in PMI's favor. PMI has since sought a lien on Keith's Georgia property in a last ditch effort to get its money.

Calls to Mr. Sweat were not returned.

We wish Mr. Sweat all the best.  He is TRULY one of our favorites and we're sure he'll find a way out of this situation!