Park, who won gold in the 400m freestyle in Beijing but was handed an 18-month doping ban in 2016, earned his spot on the team for the Aug. 18-Sept. 2 Games in Indonesia at the national team trials in April.
However, he said in a statement issued by his agency that he was not swimming well enough to compete.
"I've realised that I am in no shape to post good records," Yonhap News quoted Park as saying. "Rather than saying I am retiring, I'd like to take some time to think about my future."
The 28-year-old double world champion has six Asian Games golds to his name from Doha (2006) and Guangzhou (2010). He was stripped of a silver and five bronze medals from the 2014 Games due to his doping suspension.
(Writing by Peter Rutherford; Editing by Amlan Chakraborty)
