J.R. Smith is playing some of the best ball of his career down the playoff stretch. It couldn't have come at a better time, either. Smith will be a free agent after the season and he's trying to get paid. In addition, he's currently facing a $48,000 lawsuit for losing a necklace featuring the face of the black Messiah according to TMZ.

A jewelry company called Lemmerman's sued Smith, claiming he ordered a bunch of bling back in 2010 -- including a diamond chain, two Black Jesus pendants and some earrings -- totaling $25,500 ... but never paid.

We're told one Jesus pendant and chain cost roughly $15,000 alone.

Lemmerman's sued for $48,101 -- which includes the jewelry bill plus interest and attorney's fees -- but Smith never responded to the suit ... so a judge ruled in Lemmerman's favor.

Smith has now been ordered to pay the $48,000 asap ... or else.