SEOUL, 22 May 2015 (AFP) - Choi holed five birdies, with just a single bogey, on his way to carding a 68 round that left him eight-under for the tournament, two strokes clear of compatriot Kang Sung-Hoon in second place.
Joint overnight leader, Ryan Fox of New Zealand -- son of the All Black rugby great Grant Fox -- was one stroke further back at five-under, after shooting a second round 71.
It was a strong showing by Choi who swapped the fairways for a drill ground in November 2012 when he started a 20-month stretch of military service, which is mandatory for every able-bodied South Korean male between the ages of 18 and 35.
American Garrett Sapp also managed a 68 on Friday, taking him up to fourth place at four-under for the tournament, ahead of a seven-member pack sitting on three-under.
Leading second-round scores (South Korean unless stated):
136 - Choi Jin-Ho 68-68.
138 - Kang Sung-Hoon 69-69
139 - Ryan Fox (NZL) 68-71
140 - Garrett Sapp (US) 72-68
141 - Michael Wright (AUS) 72-69, Kim Seng-Yong 69-72, Lee Chang-Woo 70-71, Park Jae-Bum 72-69, Cho Ming-Yu 70-71, David McKenzie (AUS) 69-72, Hwang In-Choon 71-70