Thailand's Ariya Jutanugarn lost her top spot to South Korea's Park Sung-Hyun, according to the latest world rankings published on Monday.
Park regained the No.1 spot after her win in Singapore on Sunday and now leads the Thai by just 0.20 points.
Ariya led after three rounds at the HSBC Women's World Championship in Singapore but finished tied for eighth.
She relinquished the top ranking after an 18-week reign.
Park previously held the world No.1 spot for 10 weeks, from August to October 2018 before being dethroned by Ariya.
Park first appeared at the top of the world rankings in November 2017 but held the position for only one week.
She is the fourth South Korean player to reach No.1 in the history of the rankings, along with Shin Jiyai, Park In-Bee and Ryu So-Yeon.
Meanwhile, Ariya's sister Moriya remains at No.19, while Pornanong Phatlum dropped one place to No.52 and Thidapa Suwannapura moved up to No.92.
On the men's side, Dustin Johnson officially regained the No.1 ranking from Justin Rose on Monday following his triumph at the WGC-Mexico Championship a week ago.
The American cruised to a five-shot win in Mexico City at the end of last month to make it 12 straight years that he has won at least one PGA Tour event.
The 34-year-old replaces Englishman Rose by the narrowest of margins -- 0.0008 average points -- in top spot, a position he has held for 81 weeks in his career.
Brooks Koepka traded places with Justin Thomas as the former moved up to third.
Rickie Fowler jumped to seventh as he climbed above Xander Schauffele and Jon Rahm.
