Rihanna is living it up for her 25th birthday, and has no worries about what folks have to say about it.  Check out a pics of Chris Brown popping up on her Hawaiian vacay today inside...

Looks like these two lovers are on again.  Breezy made his way across the Pacific to meet up with a fishnet & bikini wearing Rih Rih in Hawaii, where she and her crew have been pouring it up and smoking it up for her b-day.  And the twosome were spotted holding hands and cuddled up in deep convo while walking along the water.

The bad gal Instagrammed a pic of herself and Mr. Brown, who is working on his sixth album, having some fun in the car as they rode around the island.  And her bestie Melissa posted some pics of the gals having some crazy sexy cool fun as well:

We're sure that "Birthday Cake" remix will get played...and re-enacted...more than a few times on this trip.  That's how they ball out.

Pics: Instagram/Splash