Yang finished with an eight-under 64 but that was only good enough for a share of third, while Jutanugarn produced a stunning approach on the final hole to finish with a birdie and sign for a nine-under 63 and 22-under for the tournament.
Even that seemed like it might not be enough, as 18-year-old phenom Atthaya Thitikul sat at 22-under with two holes to play, including an short par-five final hole.
Thitikul, who beat Ko's record as the youngest golfer to win a professional tournament when she won in Thailand in 2017 aged 14, had produced a flawless round, but she missed a short par putt on 17, before her similarly makeable birdie putt on the last also slid by the hole, denying her a playoff and sending Jutanugarn into tears of joy as she claimed victory at her home event, and her first since 2018.
The final hole was played after a weather delay of over an hour, which also disrupted Ko's finale, but when she returned she produced a lovely chip to finish with a birdie and ink a one-under 71.
Of the top 30 players at the end of the tournament, only one had a final round worse than Ko as she faded down the stretch, but the 24-year-old still produced another solid overall showing to further display her contention credentials.
After a busy run of events, Ko will now take three weeks off to prepare for the US Open in early June.