Tekashi 6ix9ine Links Up with Akon for 'Locked Up' Part 2

Tekashi 6ix9ine found himself his first musical ally outside of prison -- and it's already proving to be fruitful ... with a remix on the horizon that'll get your 2000s taste buds tingling.

The rapper just posted a video of himself with none other than Akon, and it looks like the 2 of them laid down a new track that's actually an oldie, only refreshed with T69's own verse. Yes, we're talking Akon's iconic tune, "Locked Up," which now features Tekashi.

You can hear a bit of Tekashi's bars -- he raps about feeling regret and trying to strike the best deal possible for himself via his lawyers ... and also wanting to see his daughter again. Here's the thing though ... 6ix9ine is still stuck on his trolling ways (sorta) 'cause while he teased the track, he only promised to fully release it if he racked up 100k comments.

He writes, "100,000 comments if you want this 🧡❤️💚💛💜💙🖤🤍LOCKED UP PART 2 IM ON ALBUM MODE 💿💿💿 THIS ALBUM GOING CRAZYYYYYYY 🔥🔥🔥 @akon." Something tells us he'll get those comments. The post already has 2 million-plus views, and it went up less than an hour ago.

It's interesting ... Akon seems to be the first rapper to hop on the train and get in the studio with the rainbow-haired MC -- which is REALLY colorful right now. We'd heard from several different artists over the past year or so on whether anyone would work with him again.