BANGKOK, 11 Jun 2015 (AFP) - Making light of the sweltering temperatures, Kim hit four birdies on the front nine and three more as he headed back to the clubhouse to gave himself a narrow one stroke lead over local boy, Panuphol Pittayarat.
Australian Joshua Younger sat one shot back overnight, after making a 67, and is nicely poised going into day two of the joint-sanctioned OneAsia and Japan Golf Tour Organisation event near the Thai resort city of Pattaya.
"I am happy to be leading the tournament," 35-year-old Kim said according to a statement.
"The heat is unbelievable and I had to keep my focus. However, I am used to conditions in Thailand as I train here over the (Korean) winter... I am really comfortable playing here."
Closest rival Panuphol, better known by his nickname 'Coconut', dropped a shot on the 18th to miss out on a share of the overnight lead.
Nonetheless he was pleased with his game after an inconsistent year.
"This is my best day of the year so far. I have been struggling with my putting and tee shots and my chipping a bit. I have been practicing hard and it has been paying off," said the 22-year-old from Bangkok.
65 - Kim Hyung-Sung (KOR)
66 - Panuphol Pittayarat (THA)
67 - Joshua Younger (AUS)
68 - Tirawat Kaewsiribandit (THA), Lee Sang-Hee (KOR) , Lee Chang-Woo (KOR) , Kim Bi-O (KOR) , Yan-wei Liu (CHN)
69 - Jazz Janewattananond (THA), Chapchai Nirat (THA) , Danny Chia (MAS) , Yoshinobu Tsukada (JPN) , Prom Meesawat(THA) , Hidemasa Hoshino (JPN) , Moon Kyong-jun(KOR) , Ryan Dillon (USA) , Michael Wright (AUS) , David Mckenzie (AUS), Lee Kisang (KOR) , Wang Jeung-Hun (KOR) , Stephen Dartnall (AUS) , Zhang Xin-jun (CHN)