Shin made light of the windy conditions to record two birdies and a bogey at Dundonald Links on Saturday and move to a 12-under 204 for the tournament. It was her fifth consecutive round under par at this event.
The 33-year-old South Korean is bidding for her first LPGA Tour win since capturing the now-defunct Volunteers of America Texas Shootout 10 years ago.
The last LPGA Tour player to go 10 or more years between official victories was Vicki Fergon - 12 years and three months between wins at the 1984 S&H Golf Classic and the 1996 Michelob Light Heartland Classic.
"I've never been in this position (a five-shot lead), so I don't know how to feel (on Sunday)," Shin said. "I'm going to go and practise for a little bit and get a good feel for tomorrow so I'm not such a mess in the morning."
Shin made a birdie on the sixth hole and answered a bogey on the 10th hole by making another birdie on the 11th.
"That was a very tough round. I was quite nervous for the first five holes, so I'm really glad that I was able to finish the day in red numbers," she said. "It was a pretty boring and nerve-racking day at the same time.
"That was a bit of a hiccup on the 10th. I changed my set-up this week because of all the wind and, out of habit, I lined up the putt and went back to my old set-up. I shut the face. I knew what I was doing, so I was able to get back pretty easily."
Shin holds a five-stroke lead over Thailand's Pajaree Anannarukarn, who had three birdies during her bogey-free round of 69.
"I would say almost everything went well," Anannarukarn said. "I was driving the ball well and hitting it good out there. The putter was very hot today, so that was the key. It was a challenging day, and also, at the same time, I had good fun battling with the wind. It was a great day out there."
Japan's Erika Hara (71) and Germany's Esther Henseleit (73) share third place with five-under for the tournament.
Just seven players are under par after 54 holes, with world No 1 Nelly Korda joint-29th on five-over, one better than defending champion Lottie Woad.
Grace Kim (74-70-76) is the leading Australian. The 2025 Evian Championship winner is tied 24th at four-over par.
Hannah Green (74-76-74) is tied for 47th on eight-over and Robyn Choi (76-73-79) is 12-over, in joint 56th.
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