Ray J's New Song, 'Never Shoulda Did That' -- Kim K Sex Tape Regrets (VIDEO)

Regrets ... Ray J's had more than a few, and he lays them all out in a new song that includes a not-even-thinly veiled shot at his ex sex tape partner Kim Kardashian.

In "Never Shoulda Did That" ... Ray confesses and sorta apologizes for a bunch of crap. But the line that will have Kim's ears ringing -- "f***ing bitches on camera, shouldn't a did that s***."

He also cops to taking drugs, fighting in clubs, yelling at friends, and cheating on his GF Princess Love -- who makes a cameo ... we're told that's her drunkenly weeping on a voice mail in the song.

Here's the thing ... Ray J may sing he shouldn't have banged Kim, but we know his bank account screams otherwise. He's still making coin off of "Kim K Superstar."