Jack Osbourne may have spent two months in rehab for drug and alcohol problems in 2003, but he's not down for the count.

The 19-year-old son of Black Sabbath rocker Ozzy Osbourne knocked out his veteran opponent in the second round of a muythai match on Wednesday night (April 27) in Thailand, reports the AP. The triumph came after nearly four weeks of training at a boxing camp and physical detoxification consisting of colonic irrigations.

Proud parents Ozzy and Sharon flew in to Thailand to watch their son take on experienced Thai boxer known only as "The Man." The bout only lasted through eight seconds into the second round. Muythai fights are typically comprised of five three-minute rounds. "I was very impressed with his training," says Osbourne's trainer Philip Wong. "He behaved and he trained so hard for it ... he lost 20 pounds when he was with me." Jack still aims to shed 10 more pound to achieve his prime fighting weight.

"At first mum and dad were a little concerned," says Osbourne. "But once they came here and saw the training programs -- and saw for themselves that I was mentally and physically well prepared -- they were very cool about it all."

After deciding to clean up his act after rehab, Jack took up muythai and even gave up drinking in 2004. His recent intense training is aimed at helping him shape up for an upcoming rock climbing expedition in the U.S.

Jack became a celebrity of sorts after appearing on the MTV reality show "The Osbournes" with his parents and sister Kelly. He's also made guest appearances on "Dawson's Creek" and "That '70s Show" and leaped to the big screen in the Olsen Twins movie "New York Minute."