According to the Gyeonggi Nambu Provincial Police Agency, the 33-year-old Park began to admit most of the drugs charges against him in questioning that resumed in the morning.
Park had stubbornly denied the charges until a local court approved an arrest warrant for him on Friday.
"I have had a fear about giving myself up. But I have now come to think that I have to admit what I have to admit and apologize for what I have to apologize," Park reportedly told police investigators on Monday morning.
Park is accused of purchasing 1.5 grams of methamphetamine on three occasions between last February and March together with Hwang Ha-na, the arrested granddaughter of the founder and honorary chairman of Namyang Dairy Products Co., and of using the drug five times.
The police agency requested an arrest warrant for Park after the National Forensic Service detected a trace of methamphetamine, a banned substance in South Korea, in his body hair last week.
Park faced drug allegations after the 31-year-old Hwang was arrested on April 6 on charges of selling methamphetamine and using the illegal substance in 2015.
In 2017, Park announced his plans to marry Hwang after dating her since 2016, but he later called off the marriage and broke up with her in 2018. (Yonhap)