TOKYO, September 28, 2013 (AFP) - The 27-year-old, who has not missed a single cut in Japan this season, overcame tough playing conditions at the Ibaraki Country Club to sink four birdies against one bogey for a total seven-under-par 206.
Asia's only male Major champion Y.E. Yang, also of Korea, sank a 15 footer eagle putt on the last for a 69 to share second place with Japan's Tetsuji Hiratsuka (71), Masahiro Kawamura (71) and Akio Sadakata (68).
Overnight leader Pariya Junhasavasdikul of Thailand slipped back to tied sixth after posting a disappointing 74 to trail Park by three shots at the Y150 million ($1.48 million) event sanctioned by the Asian Tour and Japan Golf Tour.
Park has enjoyed an excellent season in Japan after changing to a new putter earlier this year which resulted in him winning in September and posting three runner-up finishes.
"I struggled with my putting last year and I changed to the mallet putter and it really helped me out. I started off well in the season and that gave me a lot of confidence," he said.
Of Sunday's final round, he added: "It is going to be another day and another 18 holes. I just got to focus on my game.
"It doesn't matter who I'm playing against. I'm feeling pretty comfortable with my game so I should be good."
Scores after round 3 (par 71):
206 - Park Sung-Joon (KOR) 71-67-68
208 - Akio Sadakata (JPN) 75-65-68, Y.E. Yang (KOR) 71-68-69, Masahiro Kawamura (JPN) 69-68-71, Tetsuji Hiratsuka (JPN) 71-66-71
209 - Brad Kennedy (AUS) 72-66-71, Song Young-han (KOR) 69-69-71, Pariya Junhasavasdikul (THA) 65-70-74
210 - Kazuhiro Yamashita (JPN) 73-67-70, Wade Ormsby (AUS) 72-67-71.