Blake Griffin -- Beach Reconciliation ... With Smokin' Hot Baby Mama

Seems Blake Griffin is back ON with Brynn Cameron -- because the two spent Labor Day weekend TOGETHER ... hangin' out on the beaches of Hawaii with their adorable kid.

As we previously reported, Blake and Brynn have been on-and-off over the years ... and were definitely not together last year when Brynn gave birth to their son Ford.

But all signs pointed to "couple" in Hawaii ... where the two put every other vacationing couple to shame with their insanely ripped physiques.