Things are heating up between Khloe Kardashian and boyfriend Tristan Thompson!

The denim-darling, 32, brought her baller boyfriend, 25, back to LA after the Cleveland Cavaliers played on Sunday. The sneaked in, during the dark of night -- at midnight -- by private jet. The kept their rendezvous on the down-low, staying away from the usual dinner and club hotspots in favor of a weekend at Khloe's Calabasas mansion.

What they DID do Sunday night was to pop over to Kris Jenner's house for dinner. Of course it's not the first time Tristan's met the family matriarch, but we're told as the young couple's relationship heats up, Tristan is increasingly concerned -- as is Khloe -- with mama Kris being on board with their relationship. Our source tells us: "Khloe's paving the way for Tristan to ask for her hand in marriage. She wants him to feel comfortable around Kris so he can propose when he's ready -- she knows it's coming."

Oh lord, another baller hubby!