Parmelee will continue to be monitored by team doctors, and is considered day to day.
He was hit by a 93-mph fastball from Thomas in the sixth inning of Wednesday's 7-6 loss to the Red Sox, and stayed on the ground for a few minutes before walking off the field with the help of team trainers.
"It made a loud sound and hit him solid, but fortunately the ball went up, which means it ricocheted and kind of glanced," Twins manager Ron Gardenhire said after Wednesday's game. "It was hit solid, but we're just lucky the kid is OK."
After a day off on Thursday, the Twins return to action on Friday against the Royals at Target Field.
Parmelee, 24, is batting .260 with four doubles and a triple in 15 games this season. He's seen time at first base, left field and right field.