Chris says he's definitely had lengthy discussions with JT, JC Chasez, Lance Bass, and Joey Fatone about the band's future -- and it's just a matter of getting everyone on the same page about what they wanna do next.

He confirms to us they're working on it, and it's not a categorical no to a stage comeback -- much to the delight of tour promoters and music labels eager to cash in on the guys getting back together.

CK says if they were to reunite, it would be all fun and games 'cause when all 5 of them are in the same room, it feels like no time has passed in 25 years.

The singer also discusses more *NSYNC-related news on his podcast, "Name Drop With Chris Kirkpatrick And Brian McFayden," which has season 2 dropping Tuesday.

His first guest of the season is Backstreet Boys' AJ McLean, and Chris tells TMZ they revisit their past beef during the episode and delve into other shared boy band experiences.

As for an *NSYNC reunion ... it's been buzzing in the minds of music industry insiders for a while now, especially after the group received so much love and support last year when they reunited for a song in the latest 'Trolls' movie.