Prison Bae Jeremy Meeks' Heiress GF Chloe Green Wearing Shiny Ring

Jeremy Meeks is the undisputed rebound champ ... IF the massive rock on his heiress GF's hand is indeed proof he's locked her down.

The felon-turned-model and Chloe Green -- whose father has a $5 BILLION empire -- hit up Nobu Tuesday in Malibu tamely holding hands, and perhaps ... tried to hide her new bling

But Jeremy and Chloe posted a video of themselves all over each other, and Chloe's ring -- which looks awful engagement-y -- was blindingly obvious. It may appear to be on her right hand, but remember it's a selfie so the image is flipped.

The fast lane seems to suit Jeremy. He filed for separation from his wife just last month.