South Korean amateur Kim Hui-soo carded a six-under 66 to take a surprise lead after the opening round of the Maekyung Open in Seoul.
The 19-year-old, playing in just his first professional tournament, lit up the greens on the front nine with three consecutive birdies from the fifth and followed that up with another hat-trick from the 12th.
He bogeyed the par-four 15th, but regained his composure to birdie the 16th and finished his round on six-under, one shot clear of a group of four men tied for second.
"On the first tee I was nervous, but also excited. More excited than nervous. But I know as an amateur, I have nothing to lose," said Kim.
"I won once last year in an amateur tournament and last year I averaged inside the top 15, but this year I am playing much better."
American David Oh joins a South Korean trio including 2007 champion and last year's runner-up Kim Kyung-tae, Choi Ho-sung and Cho Min-gyu in second place.
"Things went well. I had a game plan and I stuck with it and fortunately things panned out," said Oh, whose 67 on Thursday was in stark contrast to his opening 82 last year.
Australia's Ashley Young is a shot further back on four-under, tied for sixth with South Koreans Kim Yeong-Su and Park Sang-hyun.
A chasing pack of seven are on three-under, headed by 2009 champion Bae Sang-moon.