SINGAPORE, 8 Mar 2015 (AFP) - On a day of iced towels and umbrellas, the South Korean stayed cool in the Singapore heat for two-under-par 70 and a two-stroke win over Ko as she finished the week bogey-free.
Park's scores of 66, 69, 68 and 70 and aggregate of 15-under 273 were too much for Ko, 17, golf's youngest ever number one who was unable to erase her two-shot overnight deficit.
"That's a big accomplishment for me," said Park of her accomplishment of leading the $1.4 million tournament from start to finish.
"I think I've done that probably once before only, and to have a pressure every day since Thursday, I think it's something that I should be really proud of."
New Zealand's Ko, playing with her left thumb strapped, missed short par putts on eight, 12 and 13 but finished with a curling, 12-foot birdie on 18 in front of a packed gallery.
World number three Stacy Lewis put her ball into a tree on 12 and then found water at the last before finishing on 72, four shots back in third at par-72 Sentosa Golf Club.
"She played great all week," Ko said of Park. "No bogeys around here and on a course where you can hit a good shot and you can get bad luck.
"She made no bogeys, that's pretty phenomenal."
Starting the day two strokes adrift, Ko birdied four and five to draw level with Park, whom she demoted to world number two when she seized the top ranking last month.
But Ko's bogey at eight signalled a mid-round stumble with three dropped shots, before she recovered with a birdie on 15 and another at the last after escaping from two bunkers.
Lewis had a helter-skelter final day when she scrambled brilliantly on eight and then saw her second shot on the par-five 12th nestle in the branches of a palm tree.
The American somehow escaped with par and birdied 13 as she threatened to beat Ko into second spot -- before dunking her approach into the greenside lake on the par-five 18th.
Meanwhile Park's progress was serene and she needed only birdies on seven and 11 before being doused with champagne as she toasted her 13th LPGA win and first of the year.
"I'll probably play a lot more with Lydia, a lot more often," Park said. "I just can't believe that I'm playing with somebody who can't even drink."
Final scores from the HSBC Women's Champions at Sentosa Golf Club in Singapore on Sunday (par-72):
273 - Park In-Bee (KOR) 66-69-68-70
275 - Lydia Ko (NZL) 68-70-67-70
277 - Stacy Lewis (USA) 69-69-67-72
278 - Ryu So-Yeon (KOR) 70-69-69-70, Azahara Munoz (ESP) 70-67-70-71, Feng Shanshan (CHN) 70-71-68-69
279 - Caroline Masson (GER) 71-68-72-68
280 - Carlota Ciganda (ESP) 69-66-74-71, Lee Il-Hee (KOR) 72-72-71-65, Anna Nordqvist (SWE) 69-70-68-73