Leishman and Ripper CG teammate Lucas Herbert were the leading Australians at six shots off the pace after day one at the Jack Nicklaus Golf Club Korea on Friday.
Taylor Gooch of Smash GC and Crushers GC's Bryson DeChambeau shared the lead after shooting seven-under 65s on Friday.
Louis Oosthuizen, of Stinger GC, and Cleeks Golf Club's Richard Bland were a stroke further back in a share of third place, ahead of a four-way group two shots adrift at four-under.
Leishman made a blistering start, taking a birdie three at the fourth before sinking his tee shot on the 172-yard fifth, and making a birdie two at the eighth to be four under.
But a bogey five at nine and a double-bogey at the par-four 11th helped consign him to his moderate round.
It was Leishman's fourth career hole-in-one in competition, and sixth overall.
Herbert turned at two-under after a blemish-free front nine, before bogey fives at the 10th and 16th offset his sole inward birdie at the long 15th.
Cameron Smith was the next best Australian after a one-over 73 left him in a tie for 32nd place, his three birdies offset by four bogeys.
Leishman's ace was matched by that of Stinger GC's Dean Burmester, who needed just one shot on the 205-yard 13th en route to the 68 that left him tied for fifth.
American Gooch said he hoped his superb round would reignite some of his best form from two years ago.
"Hopefully this round kind of kick-starts a good rest of the season and we can kind of channel some of that 2023 season again," he said.
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