South Korea\'s Kang Kyung-Nam tightened his grip on the Kolon Korea Open with a two-under par 69 Friday on day two of the event, giving him a three-shot lead going into the weekend. Kang is the only player to go two rounds under par at the Woo Jeong Hills Country Club course south of Seoul. Alone in second place in the $900,000 OneAsia competition is two-time champion Kim Dae-Sub, only recently discharged from 20 months of military service, who fired a 68 to go with his first-round 72. Sharing third at level par are American Charles Hong Chang-Kyu (71-71) and Korean Choi Ho-Sung (71-71), according to a press release from organisers. Y.E. Yang -- the first player from Asia to win a Major -- was a shot further back in fifth with Brazilian Lucas Lee. Kang, who has had two top-three finishes in OneAsia tournaments already this year, went on the defensive after bogeying the third and credits a hot putter for keeping him ahead of the pack. \"You can\'t be too aggressive here,\" said the 29-year-old, who has needed just 52 putts over 36 holes. \"You just have to get the ball on the green and then take your chances.\" He said he had expected a winning score of around eight to 10 under par ahead of the tournament, but had revised his estimate to seven or eight after seeing how tough it was. Second-placed Kim had to stow his clubs for nearly two years while undertaking compulsory military service, but returned to winning ways last month, just three weeks after being discharged, with victory at the Dongu Promi Open. \"I had no expectations to do well because I have only just started playing again,\" said Kim. Leading scores: 137 - Kang Kyung-Nam (KOR) 68-69 140 - Kim Dae-Sub (KOR) 72-68 142 - Hong Chang-Kyu (USA) 71-71, Choi Ho-Sung (KOR) 71-71 143 - Y. E. Yang (KOR) 73-70, Lucas Lee (BRA) 72-71 144 - Kim Dae-Hyun (KOR) 71-73, Lee Seong-Ho (KOR) 74-70, Ryu Hyun-Woo (KOR) 75-69, Hwang In-Choon (KOR) 74-70, Kang Wook-Soon (KOR) 73-71