Hamilton was called for a flagrant foul penalty one during the game, but the league upgraded it to the more severe level two on Monday.
Hamilton and Redd became tangled with 5:48 left in the fourth quarter and the Bucks leading by 20. Hamilton spun around and hit Redd in the mouth with his elbow.
Hamilton -- who tapped Redd on the leg at the foul line after the play in an apparent gesture to show that he didn't hit him intentionally -- said the league didn't give him an explanation for the change.
"Hopefully, I can talk to someone -- $15,000? I don't understand that one. ... I don't think that was fair," Hamilton said.
Hamilton won't be suspended for the incident, but severe fouls earn points toward a potential suspension.
"Rip's not a guy that's going to get a lot of flagrants, so that's not going to affect him," Pistons coach Flip Saunders said.
Bucks coach Terry Stotts declined comment.