INCHEON, 19 Oct, 2014 (AFP) - Baek made birdie on the first playoff hole to defeat American Brittany Lincicome and fellow South Korean Chun In-Gee on the par-72 Ocean Course, at the Sky 72 Golf and Resort club in Incheon, South Korea.
She took home US$300,000 in the winner's cheque.
Baek, who turned 19 last Wednesday, became the eighth South Korean winner of the tournament, which was inaugurated in 2002 as the nation's only LPGA stop each year.
It was also the third straight year in which the winner was determined in a playoff.
The three playoff participants ended the regulation tied at 10-under 278.
Lincicome and Chun each carded a 66, while Baek shot a 67 in the final round.
Chun fell out of contention early in the playoff, by putting her third shot into the water and making a bogey.
Both Baek and Lincicome sent their third shots close to the hole. Lincicome was the first to putt but just missed her birdie attempt, setting the stage for Baek's dramatic finish.
The teenager stepped up and sank the putt to punctuate an impressive comeback.
With Lincicome making three birdies and Chun pouring in four birdies on the front nine, Baek had an ordinary start to her final day.
She went out at five-under after trading in a birdie with a bogey but went on a roll on the back nine, making five consecutive birdies starting on the 11th hole.
Baek saved key pars on the 16th and 17th, before missing a short birdie attempt on the 18th to get into the playoff.
She faced a birdie putt of a similar length in the playoff and did not miss the second time.
"I was so far back after the front nine that I didn't really expect to win," she said. "I was just playing catch up on the back nine and trying to enjoy myself out on the course."
World number two Park In-Bee finished one stroke out of the playoff at nine-under, after shooting a 67 -- she could have supplanted the absent Stacy Lewis as the top-ranked female golfer with a victory.
Michelle Wie and Catriona Matthew ended another shot back in a tie for fifth.
Kim Hyo-Joo, a South Korean teenager and shock winner of the Evian Championship, was alone in seventh at seven-under.
Final scores on Sunday at the LPGA KEB-HanaBank Championship:
*- denotes playoff winner
278 - * Baek Kyu-Jung (KOR) 74-69-68-67, Brittany Lincicome (USA) 70-70-72-66, Chun In-Gee (KOR) 76-67-69-66,
279 - Park In-Bee (KOR) 71-73-68-67
280 - Michelle Wie (USA) 76-70-67-67, Catriona Matthew (SCO) 69-74-70-67,
281- Kim Hyo-Joo (KOR) 72-72-71-66
282 - Austin Ernst (USA) 76-71-69-66, Gerina Piller (USA) 73-70-71-68, Lee Il-Hee (KOR) 69-72-71-70, Beatriz Recari (ESP) 70-70-72-70,
283 - Ryu So-Yeon (KOR) 76-69-70-68, Angela Stanford (USA) 74-71-68-70, Sandra Gal (GER) 70-71-71-71, Suzann Pettersen (NOR) 70-71-71-71, Karine Icher (FRA) 71-68-73-71, Bae Hee-Kyung (KOR) 70-73-68-72
284 - Lee Mi-Rim (KOR) 69-74-73-68, Katherine Kirk (AUS) 74-72-69-69, Julieta Granada (PAR) 71-72-72-69, Cristie Kerr (USA) 72-72-69-71, Pornanong Phatlum (THA) 73-70-69-72, Heo Yoon-Kyung (KOR) 72-70-70-72