Ruffels' chances were fading before she rattled off four birdies in her last five holes to be outright fourth, two shots behind leader Jenny Bae going into the final round of the Mexico Riviera Maya Open.
The 25-year-old, second-year LPGA player posted a one-under 71 on the El Camaleon course at Mayakoba on Saturday to get to five under.
It was the second day in row she had roared home with birdies at holes 14, 16, 17 and 18.
American tour rookie Bae bogeyed the last hole as she also shot 71 and led by one from China's Yahui Zhang (68) and Japan's Chisato Iwai (68).
Ruffels was three over for her round when she holed a 15-foot birdie putt on the 14th hole. On the par-4 16th, the toughest on the back nine, she holed a birdie putt from 20 feet.
Ruffels left her tee shot just in front of the green on the 17th, pitched to a back pin some 4 feet away for birdie, and then made it three straight at the end with a birdie at the 18th. That allowed her to salvage a 71 and left her very much in the mix.
"I was just proud of the way I kind of stuck in there and felt like I gave myself the chance to kind of come back," Ruffels said.
"To finish the way I did is really good and some momentum into tomorrow."
Karis Davidson was best of the other Australians, tied 18th at two under after a 68, with Robyn Choi (69) a further shot back and Sarah Kemp (74) at five over.
The El Camaleon course at Mayakoba was set up for scoring, with the tees moved up on the par-4 17th to make it reachable with a fairway metal, and the par-5 closing hole.
Zhang finished birdie-birdie and Iwai also birdied the last two holes.
Bae was pleased to still be in front after playing the bacj nine in one over.
"I feel like I definitely left a few birdies out there, but it's OK because I know those chances that I missed today could also be the birdies that I get tomorrow," Bae said.
This is the final week before the US Women's Open, and the LPGA's return to Mexico for the first time since 2017 did not attract a strong field with Charley Hull at No.15 the highest-ranked player.
But it's a great opportunity for everyone else. The top 11 players on the leaderboard — everyone at 4 under and better — are going for their first LPGA win.
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