Still battling a wrist injury that derailed her 2022 season, Ko burst into tears after her triumphant return at Sentosa as she finished with a 17-under par total of 271 at the no-cut tournament with a $1.8 million prize purse.
Ko was unflappable on the front nine and although she faltered with a bogey on the 11th, she sank a 30-foot putt for birdie on the 13th and a two-foot par putt on the final hole to edge Korda (69) for her first title since last year's win.
"It's a great honour to defend this title and I had a great week, and a long week as well, with all the rain," said Ko, who will bank $270,000 for her win.
"Before this week I practised really hard. I knew I was defending so I wanted to get one more trophy. It paid off and I'm really happy."
Unlike her comeback win last year, Ko did not need a five-birdie charge in the last six holes, instead holding on to her overnight lead with a masterful display as she joined compatriot Park In-bee as the only two-time winners of the tournament.
Ko set the tone with a birdie on the opening hole and drained another on the fifth after a superb approach shot, before rolling in an eight-foot putt from the fringe of the green to save par on the 10th.
American Korda had moved to within a shot of Ko after three straight birdies from the third hole, but a bogey on the sixth and another on the 13th proved costly and effectively ended her challenge.
She secured second place on 15-under after draining a four-foot birdie putt on the final hole. Japan's Ayaka Furue (67) along with Americans Danielle Kang (68) and Allisen Corpuz (69) ended a further shot adrift of Korda in joint-third.
"Always playing with Nelly, it's very hard to compete. She's a great player and I was thinking, 'She's better than me and so I'd better learn some things from her'," Ko said. "It was a tough week but I made it!"
Top-ranked Lydia Ko of New Zealand shot 74 and was at five-under, 12 shots behind in a share of 31st.