Ray J's new music video for "I Hit It First" is finally here -- and not only is the chick in the video a dead ringer for Kim Kardashian, but she also reenacts the couple's infamous sex tape (minus the sex).

TMZ has obtained the full version of "I Hit It First" and even though J won't actually admit the song's about Kanye West's baby mama ... all 3 min and 38 seconds of doppelganger footage PROVES otherwise.

Seriously, it's not an exaggeration, it's chock-full of Kim K references ... from her reality show, to her ass, to her XXX vid.

And Ray J sneaks in some Kanye shots too ... but they're a little more subtle. Kind of.