The 45-year-old former world heavyweight boxing champion came to a rude awakening on Friday that Muay Thai is just as punishing.
"It's much harder than boxing," Bowe said after limping out of the ring.
Bowe took a big beating from his 30-year-old Russian opponent Levgen Golovin, who assaulted the former champion with repeated kicks to the shins.
Bowe lost his balance and fell five times before the bout was ended by technical knockout after his last fall.
"You can recover from a head shot or a body shot, but when you get kicked in the leg it lasts a long time," he said. "My leg is still hurting. I don't know how long it's been — 15 minutes?"
Bowe's last boxing match was in 2008. He says he decided to try Muay Thai because he was bored with retirement and needs the cash.
He made $150,000 from Friday's fight, organized by Thai promoters trying to increase the international appeal of Thailand's national sport. The bout was held at an outdoor ring set up beside the beach in Pattaya, a Thai town best known for its seaside red-light district.
Bowe beat Evander Holyfield in 1992 to become the undisputed world heavyweight champion.
Now weighing 300 pounds, Bowe was heavy and slow and barely landed a punch in Friday's fight.
Despite the pain in his legs, Bowe smiled for the cameras after the fight and mustered some optimism.
"I had a lot of fun. I'm going to do it again. Next time it's going to be different," he said. "I'll be back soon."
Bowe's opponent shook his head in disbelief when told the aging boxer isn't giving up on Muay Thai.
"It would be a big mistake. It's not for him," Golovin said. "He's too slow and a bit too old."