As many of Thitikul's challengers faltered down the stretch on Saturday, Green hung tough to eke out a three-under-par 69 in Pattaya to stay in the mix at the $US1.8 million LPGA Thailand.
At 15 under in her first start of the year, Green is tied for seventh entering championship Sunday but will need to reel in not only Thitikul, from five shots back, but a batch of other women's golf superstars to claim a sixth LPGA Tour title.
Showing her class, Thitikul rammed in three straight birdies - including on two of the toughest three holes on the Old Course - to close her round of 66 and soar to 20 under par.
After starting Saturday's moving day two strokes off the lead, Thitikul had six birdies and just one bogey in a seemingly single-minded pursuit of a hugely popular home-town triumph.
As solid as she appears, having recorded only one bogey through 54 holes, Thitikul has some capable pursuers hot on her tail.
With a third-round 65, South Korean Hyo Joo Kim is solo second at 18 under, one stroke ahead of Japanese halfway leader Somi Lee, American Allisen Corpuz and Japan's Chizzy Awai.
Finding it impossible to follow up her blazing second-round 61, Lee steadied after a horror front nine to post an even-par 72, while Corpuz (67) and Awai (68) made significant moves up the leaderboard to within three shots of the Saturday night leader.
New Zealand's former world No.1 and future Hall of Famer Lydia Ko is outright sixth at 16 under following an up-and-down moving day 69.
While Green stayed in contention, fellow Australian Grace Kim, with a disappointing round of 73, stumbled on the back nine to slip from tied 10th at the halfway mark to a share of 29th at eight under - a dozen shots adrift of Thitikul.
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