The 21-year-old Korean shot a five-under par 67 for a three round 12-under par total of 205 on the hilly 6,964 yard (6,368 metre) course at the Namseoul Country Club in the South Korean capital, the third stop on the 2012 OneAsia circuit.
Bi-o, who won on OneAsia last year when he prevailed in a four-way play-off to take the Nanshan China Masters, played blemish-free golf until the last, where pulled a sliding four-footer to give the chasers the sniff of a chance on Sunday.
Overnight leader Park Sang-hyun was alone in second place, while Hwang In-choon and Choi Ho-sung were a shot further back at eight-under.
"I tried really hard to concentrate out there and it went well all day until that bogey on the last," Bi-o said. "I just want to go out there tomorrow [Sunday] and do the same thing."
Bi-o has been one to watch since his youth when he won both the Korea and Japan amateur championships, but the rest of the world took notice in 2011 when at 19 he won full playing rights on the U.S. PGA tour -- the youngest to get his card that year.
It proved a struggle, however, and Bi-o lost his card, although at 25 on Nationwide Tour this year he is in good shape to regain admittance to the top flight.
"I think I was a little bit too eager and there was a lot of attention on me," he said. "Next time around I will be better prepared."
Bi-o said he was enjoying the relative anonymity of the Nationwide Tour where he was free to concentrate on his game.
"My priority is to get my full PGA tour card back," Bi-o said, "so if I can get into good shape on the Nationwide, I also want to play OneAsia as much as possible".
Bi-o scored three birdies either side of the turn on Saturday to stamp his authority on a tournament played in perfect weather in front of excellent crowds.
He said he had been helped by much better physical conditioning.
"Until I played on the PGA I used to exercise in the off season and not bother during the season," he said. "But once I saw how they applied themselves, I realized I had to do the same.
"I am much fitter now. Walking up these hills at Namseoul means you lose your breath, but my recovery is much quicker and this helps play your shots."
The par-five 14th proved to be the turning point of the day as Park bogeyed after twice hooking into the woods that line the course. A birdie by Bi-o meant a two-shot swing and a lead he never looked like relinquishing.
Hwang and Choi stayed in the hunt after both scoring 68s on Saturday, as did China's Hu Mu who, has a mountain to climb at seven behind, but is still on course for an excellent pay day.
With him at joint sixth place is OneAsia Q School graduate Lucas Lee, from Brazil, who charged at the leaders at the start with three birdies in the first four holes, but gave a couple back as the round unfurled.
Jason kang was the best of the Americans in the field at four-under, while Stephen Leaney led a strong Australian contingent a couple of shots further back.