The Kiwi made four birdies in a spectacular five-hole stretch and closed with yet another birdie for a five-under 67 in windy conditions at the rain-soaked Miramar Golf and Country Club in Taipei.
Ko will jump from second to first in the world with a victory or second-place finish today, while she could also seize top spot depending on the progress of current world No 1 Inbee Park at the LPGA's KB Financial Star Championship South Korea.
Having already spent 19 weeks on top of the rankings in 2015, Ko's spectacular year would continue with a positive result. The 18-year-old triumphed at the Evian Championship in France last month to become the youngest major champion in women's history, while she and Park are currently tied for both the tour victory lead with four and the lead in the player of the year points race.
If Ko holds her nerve to claim victory today, it would be her 10th on the LPGA Tour to sit alongside four other worldwide wins, including at the 2013 Swinging Skirts World Ladies Masters on the same course.
Her familiarity with the conditions at Miramar has certainly paid dividends so far this week, with Ko leading on a 13-under total. Having opened the tournament with a three-under 69 to sit seventh, Ko charged up the standings with a second-round five-under 67 to sit within one stroke of the lead heading into yesterday's play.
Ko pulled level with South Korea's Eun-Hee Ji with a 6m birdie chip on the 11th, streaking two strokes ahead with a 2.5m birdie putt on the 12th. She followed that up with a 4m putt from the fringe on the 14th and a 3.5m putt on the 15th to push her advantage to four shots.
And, after Ko matched Ji with a birdie on the 18th, holing an 2.5m putt after reaching the fringe in two, she left herself with a golden opportunity to reclaim the No 1 ranking. The teenager's form comes as no surprise after displaying typically fine form in recent weeks, finishing outside the top four just once in her last seven LPGA Tour events.
