NBA's J.R. Smith: Super Santa Son ... Bought Mom A House For XMAS!!!

J.R. Smith totally out-Santa'd St. Nick in the gift giving dept ... at least according to his mom who says the Cavs forward spoils her every Xmas with expensive bags, fancy cars ... and even a freakin' HOUSE.

We ran into Ida Smith -- who was in NYC working with the J.R. Smith Family Assist Foundation -- and being that it's the yuletide season we had to ask ... what's the best gift her super rich son left under the tree?

When we say super rich we mean it ... J.R.'s made over $40 million during his NBA career so he's definitely got the paper to make the holidays special.

Check out the clip ... Ida says Smith never disappoints, with her past holiday haul including a Louie bag, a brand new BMW, and on one faithful Christmas eve 10 years ago ... A BRAND NEW HOUSE.