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.