Chris Brown is back to his old ways! The jailbird hit up a Malibu beach party yesterday with girlfriend Karrueche Tran, to celebrate the Fourth of July with some friends. We just hope he's staying straight!

Seems Breezy's keeping his cool with some down-time with Karrueche ... and he's not shy about sharing! CB posted a shot of Tran on his bed in a thong and let's just say it's from an interesting angle.

Earlier, at the party, Brown brought some flash, arriving in his $400K Lamborghini Aventador, the singer wore an unusual get-up -- a hippie poncho-style shirt with a strange gold-dipped dinosaur skeleton necklace, black-and-red Air Jordans, topped off with a baseball cap. Chris and Karrueche also stopped by the 1Oak party at Nobu Malibu and Chris posted this shot of him and Tyga, captioning the shot "#fanofafan nobu! Happy 4th!"