Lance Bass says he's not rich from his *NSYNC days ... revealing the group members made basically no money despite sold-out tours and hit records.

The singer-songwriter appeared on "The Zach Sang Show" earlier this week ... during which he got into the group's finances at the height of their fame -- saying they had a $35 per diem, and that's about it.

Eventually, Lance says the group members got their first check -- this at the height of their fame -- for only about $10,000.

Lance says this was after the group had made their record company millions ... especially via merchandising, which Lance seems to indicate they didn't get a dime from.

He adds he's especially upset with the adults who were in the room for telling the teens to just do their dang jobs ... instead of standing up for them.

Don't worry too much about Lance, though ... he says he's done well for himself in the years since -- this despite the stigma that many boy band members have faced after their time with the group ends, he says.

As for any regrets ... Lance says he wishes *NSYNC would've kept working together like the Backstreet Boys -- instead of breaking up back in the day.

Bottom line ... don't be shocked to see Lance or the other *NSYNC guys working hard still -- the band didn't set them up for good.