SEOUL, Oct 5, 2012 (AFP) - Choi, the tournament host, started his second round five shots behind overnight leader Ryan Yip of Canada but hit four birdies in his first six holes and made the turn in 32, holing another four birdies before the light dwindled.
"When I got my first birdie on the opening hole, the confidence started coming back and I had this feeling that I was going to do very well today," said Choi, 42, who is on 10-under par after 14 holes of his second round.
A round of 64 from 23-year-old Chinnarat, including eight birdies, gave him the clubhouse lead, putting him in a strong position to end his three-year title drought with a two-day total of 10-under-par 132.
"It was really cold when I started on the first hole. I hit my first shot onto the fairway but hit a bad second shot. I managed to recover quickly by hitting a lot of good shots and I also managed to putt well," said Chinnarat.
Chinnarat -- the Asian Tour's youngest winner when he won his first title just days after his 17th birthday -- has a total of three Tour wins.
South Korea's Lee Sung struck a 68 for a share of third place with Yip, who posted a 71 after fog led to the loss of two hours' play at the Haesley Nine Bridges Golf Club.
Leading completed scores after round two:
132 - Chinnarat Phadungsil (THA) 68-64
135 - Lee Sung (KOR) 67-68, Ryan Yip (CAN) 64-71
136 - Kim Dae-Hyun (KOR) 71-65
137 - Lee Kyoung-Hoon (KOR) 69-68, Charlie Wi (KOR) 67-70
Selected scores
K.J. Choi (KOR) -10 through 14 holes
Ben Curtis (USA) -6 through 14 holes