The final-round Australian charge never materialised as Boutier denied Thai prodigy Atthaya Thitikul in a dramatic and near-record-setting sudden-death playoff at the $US3 million ($A4.7 million) Maybank Championship in Malaysia.
It took a birdie from Boutier on Sunday's ninth extra hole to see off Thitikul, the precocious youngster who reached world No.1 last year as a teenager.
"I'm just so happy it is over really. It was such a long day, a long week in general and I couldn't be prouder of my performance this week," Boutier said after surviving nine hours, 27 holes and a two-hour storm-enforced delay to get the job done.
The 29-year-old had looked poised for victory hours earlier after seizing the clubhouse lead with a brilliant eight-under-par 64.
But Thitikul birdied the last hole for a 68 to force the playoff, with both players finishing with 21-under totals of 267 at Kuala Lumpar Golf and Country Club.
Adding to the tension, the playoff was stopped midway through the second hole because of lightning in the area.
When it resumed, the pair couldn't be separated until Boutier rolled in her 11th birdie of the day on the par-3 15th.
Boutier's steely victory - and extraordinary bogey-free day under intense pressure - consolidated her position atop the season-long Race to the Globe standings with three tournaments remaining.
The world No.5's latest triumph followed victories this year at the LPGA Drive on Championship, the Women's Scottish Open and her maiden major at the Evian Championship in her homeland.
With a final-round 71, American third-round leader Rose Zhang tied for third at 19 under, two strokes out of the playoff, with Thailand's halfway leader Jasmine Suwannupara (70).
After two early bogeys left her too far back to challenge, Hannah Green rallied with three birdies in four holes on the back nine to close with a 71 and finish as the leading Australian in a tie for 17th at 11 under.
Compatriots Grace Kim and Sarah Kemp shared 34th spot at eight under following a pair of final-round 70s.
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