Meanwhile, Sihwan got his early birdie on his opening hole. He made further gains on holes 14 and 16 before three successive birdies starting from the third hole gave him a commanding five-shot lead at that stage.
Sihwan then dropped two shots on the sixth hole but responded quickly with another birdie on seven before signing for a two-day total of nine-under-par 133.
“I hit my ball in the waste area on six and didn't have a good lie. I tried to get too close with the long bunker shot. I thought I hit it pretty good from behind the green, but I just didn't check, and I missed the putt.
“I’ve to keep on making putts and hitting it straight as this course will get you if you don't,” said Kim.
World number 27 Paul Casey, who struggled with an opening 76, made amends with a 68 to make the weekend cut that was set at three-over par.
“I struggled yesterday, and the viewers probably know how difficult this golf course is. I played some poor golf and three drop shots in the closing holes were pretty criminal. So, I had a lot of work to do today, and I’m proud of the way I played,” said Casey.