Finishing with an eagle, the 44-year-old Scot carded a five-under-par 67 - the same score he signed for in the third round when finishing joint-seventh behind winner Matt Wallace at the same venue last year.
It was Gallacher’s lowest score of the season, earning him a place at the top of the leaderboard alongside American Julian Suri, with South African Christiaan Bezuidenhout, Spaniard Pablo Larrazabal, Swede Robert Karlsson and Thailand’s Prom Meesawat all one back in joint-third.
“I have started poorly, to be honest,” admitted Gallacher of missing the cut in five out of six outings this season, including four in a row coming into this event. “I’ve had a sort of big miss in the bag that has been costing me triples and doubles.
“I knew I was close last week (in the Maybank Championship). I played lovely, but just didn’t get anything out of it. But coming back to a place where I’ve played well hopefully I can draw on some inspiration from last year.”
The three-time European Tour winner was out in 33, helped by birdies at the second, fourth, seventh and ninth. He then started for home by making back-to-back gains at the 10th and 11th before seeing his momentum halted by a double-bogey 6 at the 461-yard par-4 14th.
However, that damage was repaired by his grandstand finish as he found the fairway with a driver off the tee at the 625-yard 18th, just missed the green with a 4-iron and rolled in the putt for a 3 to put a huge smile on his face.
“It was a perfect morning,” he added. “Cool to start with and then it heated up later on in the round, and not too much wind, so it was perfect today. “It is quite a strategic course. I don’t think you need to be the longest player on the Tour to play it. I think you’ve just got to plot your way around it.
“I think you have to get it in play off the tee, there is just so much trouble. I think if you get the tee shot in place you can hit a couple of nice iron shots and take advantage of the par-4s that are quite short, drive a couple, and knock it on to the par-5s.”
Suri, who claimed his maiden European Tour victory in the Made in Denmark two years ago, is making just his second appearance since undergoing a hernia operation that ended his 2018 campaign with two events to go.
The 28-year-old, who hit the ground running as he returned to action with a top-20 finish in the Maybank Championship, matched Gallacher’s effort by carding seven birdies, including five in seven holes on the front nine.
Richie Ramsay put a second Saltire up on the leaderboard as he opened with a three-under 69 to sit joint-seventh in a group that also includes Australian Scott Hend, last week’s winner in Malayasia, Indian star Shubankar Sharma and former Scottish Open champion Edoardo Molinari.
Marc Warren, who made a 4000-mile journey to tee up in the event after securing an invitation, sits joint-60th after signing for a one-over 73, but it was a tough debut in the event for David Law, the Vic Open champion, as he had to settle for a 78.