Born in South Hwanghae Province, Pak's first marathon race came at the Pyongyang Marathon in 2005. After racing at the Xiamen and Macau Marathon races in 2006, he dipped under two hours and twenty minutes for the first time in 2007: he won the Pyongyang race in a personal best of 2:12:41 hours and also ran at the Beijing Marathon, timing 2:15:17 hours for eleventh place. He defended his Pyongyang title in 2008 and was selected to compete in the 2008 Olympic marathon, where he placed 40th overall.