The 16-year-old Kim compiled a three-day total of 13-under 197 after marking his card with one bogey and four birdies at the two-million-baht event, co-sanctioned by the Asian Development Tour (ADT) and the All Thailand Golf Tour (ATGT).
Thailand's Suradit Yongcharoenchai, who started the round four shots off the pace, returned with a 64 to move into second place on 198 while Indonesia's Danny Masrin sits in third place following a 67 at the Laguna Golf Phuket.
Kim dropped a shot on hole two but recovered nicely with a birdie on hole three to make the turn in 35. He notched birdies on holes 10, 13 and 16 for an outward 32.
"I had a slow start and was missing a lot of key shots on the first nine holes. I missed the green left on the second hole and made bogey but I managed to get it back on the next hole with a birdie putt from five feet."
The young Korean relishes the opportunity to be playing in the final group for the first time on the ADT.
"I just wanted to be in the final group tomorrow and I did that. I will try not to think about my scores tomorrow and just try and go low," said Kim.
Suradit, 20, marked his card with one eagle, five birdies, and one bogey to put himself in contention despite battling with a flu.
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