SOUTH KOREA, 11 Sept 2015, (AFP) - Jeffress fired a second round one-under-par 70 at Woo Jeung Hills Country Club for a halfway total of seven-under-par 135.
Jeffress, who claimed the Fiji International last year on OneAsia for the biggest win of his career, rushed into a healthy early lead with three birdies, but three bogeys soon followed to allow the chasing pack to close in.
"It’s great to be in the hunt at the halfway mark," the 39-year-old said, adding his win in Fiji gave him huge confidence to go on to secure more titles.
Song, 24, who is looking for his first win as a professional, fired 67 with six birdies and two bogeys to set up one of the most important weekends of his fledgling career.
"I have been playing well and feel I am close to getting a win. A win here in my national Open would be the best," Song said.
One stroke further back were Hur In-Hoi and Park Jae-Bum, who shot 67s.
Tying for fifth on five under are Korean amateur Oh Seung-Taek and his countryman Lee Kyung-Hoon.
Leading scores (South Korea unless stated):
135 - Steve Jeffress (AUS), Song Young-Han
136 - Park Jae-Bum, Hur In-Hoi
137 - Oh Seung-Taek, Lee Kyung-Hoon
138 - Kim Geon-Ha, Ryu Hyun-Woo
139 - Kim Do-Hoon