After blowing the last of a seven-stroke lead with her second straight bogey, the Norwegian star hit a 'grip-down' 3-wood from 225 yards to 15 feet to set up an eagle putt that beat Laura Davies by a stroke Sunday in the Honda LPGA Thailand.
'I think that was the best putt of my life,' Pettersen said. 'I was just like, 'Drop! Drop! Drop! Please drop!' It was really nice. It would've been really disappointing if I let it go away.'
Pettersen's 1-under 71 left her at 21-under 267, not the number she had in mind a day earlier after reaching 20 under with a bogey-free 63, but good enough for her second straight LPGA Tour victory and third in four weeks.
'It's been three wins in October, so I can't complain,' said Pettersen, ranked fourth in the world two years after a ruptured disk threatened her career. 'I'll enjoy a week off, now, and try to sum it up and get ready for the last few.'
Davies, paired with Pettersen, birdied the final two holes for a 65. The 44-year-old English player was trying to win her first LPGA Tour title since 2001. She won a European tour event in Austria last month for her 68th worldwide victory.
'At the moment, I'm really disappointed, but overall, I'm really, really pleased,' Davies said. 'I played well this week. I putted well. I've driven it magnificently. Overall, I go away from here having great memories, but I'm very disappointed because I wanted to win.'
The dramatic finish on the hot day at Siam Country Club extended Pettersen's string of consecutive rounds at the top of the leaderboard to six. She has had a least a share of the lead in nine of her last 12 tour rounds.
'It was so warm out there today and the sweat just keeps running down your face,' Pettersen said. 'It's a different challenge. You have to stay hydrated, drink enough and eat enough. This victory is a sweet one.'
Paula Creamer shot her third straight 66 to finish third at 18 under, and Australian Rachel Hetherington (65) followed at 16 under. Stacy Prammanasudh (66) was 14 under, with Annika Sorenstam (72) another stroke back in sixth.
Creamer parred the 18th after hitting into a bunker.
'It was an unfortunate last hole,' Creamer said. 'What are you going to do? Probably not hit it into that bunker. But, I'm not going to stand there and lay up.'
Canadian Alena Sharp, two strokes behind Pettersen after each of the first two days, ended up seventh at 11 under after weekend rounds of 72 and 70.
Former Duke star Virada Nirapathpongporn topped the five Thai players in the field, shooting a 71 to tie for 22nd at 4 under. Ariya Jutanugarn, at 11 the youngest qualifier in LPGA Tour history, shot a 74 to tie for 51st.
Davies pulled even with Pettersen with a birdie-bogey swing on 17, putting Pettersen in serious danger of a final-round meltdown rivaling the late three-stroke lead she lost in the Kraft Nabisco. Pettersen missed a 6-foot putt on the par-3 16th and a 3-footer for a three-putt bogey on the par-4 17th.
The lead was down to two after Pettersen bogeyed the par-4 ninth to make the turn at 1-over 37. Davies was 4 under on the front nine, opening with an eagle and a birdie to slice Pettersen's advantage to four. Davies gained another stroke when her Solheim Cup teammate bogeyed the par-4 fifth, her first bogey since the 12th hole Friday.
Davies pulled within one with a birdie on the par-5 10th. Pettersen birdied 11 to get back to 20 under, but Davies countered on 14 to again move within one. Pettersen then birdied the par-5 15th to take a two-stroke lead that she promptly lost on 17.
Pettersen began her dominating run with a playoff victory over top-ranked Lorena Ochoa in the Longs Drugs Challenge, finished fifth in the Samsung after starting sharing the third-round lead with winner Ochoa, then won last week in South Korea in an event cut to 36 holes because of unplayable conditions.
In May, she rebounded from the Kraft Nabisco loss to win the Michelob Ultra Open for her first LPGA Tour title. She then took the McDonald's LPGA Championship in June for her first major and won a European tour event in Norway in August.
The 26-year-old player has won five of her last 15 LPGA Tour events after failing to win in her first 80 starts dating to 2001. She earned $195,000 on Sunday to push her season total to $1,753,309, second behind Ochoa's record $3,337,993.