Lydia Ko squandered a chance to head the LPGA player of the year leaderboard when she finished 20th at the Taiwan Open.
Ha Na Jang held off Shanshan Feng by a stroke in wind and rain for her third victory of the year.
With player of the year leader Ariya Jutanugarn sitting out the tournament, a sixth placing or better would have seen Ko leap past the world number two.
The 19-year-old Kiwi leads the other main categories including the world rankings, official money list and Race to CME Globe.
But Thailand's Jutanugarn has a four point lead over Ko in the Rolex player of the year race, in which top-10 finishers are awarded points. The winner gets 30 points and the 10th placed golfer one point.
Points are doubled at the five major championships. Jutanugarn has won five tournaments this year, and Ko four.
Canada's Brooke Henderson birdied the last two holes for a 70 to tie for third with South Korea's Hyo Joo Kim (69) at 10 under. Taiwan's Candie Kung (69), South Africa's Lee-Anne Pace (71) and South Korea's Hee Young Park (72) were another stroke back.
The tour will be in South Korea next week, then visit China, Malaysia and Japan.