Tom Schwartz Singing Karaoke in L.A. Amid Tom Sandoval Affair Drama

Tom Schwartz didn’t show much concern about the outrage Tom Sandovalthe relationship of Raquel Leviss — which makes this Green Day performance all the more troubling.

Witnesses tell TMZ … Schwartz was with his friends at The Oaks Tavern in Sherman Oaks for some karaoke — showing the crowd his version of Green Day’s hit, “Brain Stew.”

We’re told he picked up his group’s tab Wednesday night. It’s unclear how long Schwartz and the gang stayed, but we’re told Sandoval was definitely not in attendance.

Schwartz doesn’t seem too confused about what’s going on with his best bud right now … but he should be if you ask the former “Vanderpump Rules” cast member Kristen Doute.

As we reported, Kristen — who dated Sandoval years ago — completely dragged Schwartz calling him “f****** p****” because of his silence about his friend’s relationship. He said he expressed concern in texts, but thinks public actions speak louder.

BTW, Schwartz and Raquel are also an item, made into the current season of the show … so, there’s a little more drama.

Schwartz has been tight-lipped about the fraud — until Saturday, that is … when he sitting on the fence about who to show his loyalty to… ultimately throwing up his hands and raising it in a big bummer.