The Frenchman was playing the Creek Course at 13th Beach Golf Club and despite facing the windier afternoon conditions, he made eight birdies to get to 14 under and lead the way.
Sciot-Siegrist won the Galgorm Resort & Spa Northern Ireland Open presented by Modest! Golf on the European Challenge Tour in 2017 and agonisingly missed out on graduating by one spot last season after finishing second at the Grand Final and 16th on the Road to Mallorca.
He did not let that disappointment distract him as he went on to secure his card at the Qualifying School and will now go in search of a first European Tour title.
"It was a great round," he said. "It was similar to yesterday, I played really good golf and putted really well. Overall just a very nice round and everything is going great.
"In general, I don't have many expectations. I'm just trying to do my job, like really do what I need to do on the course and during practice rounds and everything. When I'm playing, obviously there's pressure and everything, but I'm just trying to do my best and we'll see at the end.
"There's two more days, we're only halfway. I played really good golf, hopefully it continues like that."
The morning groups had set the target at ten under and Griffin was the first man to join them from the second wave as he made a hat-trick of birdies from the second on the Beach.
Morgan made gains at the third, fourth, sixth and seventh on the Creek, and Sciot-Siegrist made it a seven way tie with birdies on the tenth, 11th, 14th and 17th.
When I'm playing, obviously there's pressure and everything, but I'm just trying to do my best and we'll see at the end
The trio then began to distance themselves from the rest as Morgan birdied the ninth from 12 feet, Griffin holed a long putt on the eighth and Sciot-Siegrist picked up a shot on the first.
Morgan and Griffin both made gains on their respective tenth holes but Sciot-Siegrist picked up a shot on the second and, when he made yest another birdie on the fifth, he had the solo lead.
An approach to eight feet put him two ahead and bogeys from Morgan and Griffin on their final holes meant the lead was up to three.
Smyth then set about reining him in, cancelling out bogeys on the 11th and third with birdies on the tenth, 15th, 17th, second, fifth, seventh and ninth.
Playing partners McLeod and Lee took very different routes up the leaderboard on the Beach, with Lee birdieing the first and third and adding further gains on the sixth, seventh and tenth before parring his way home.
McLeod bogeyed the first and second but hit back in style, picking up shots on the fourth, seventh, ninth, 11th, 15th and last.
Jarryd Felton made the third hole-in-one of the 2020 Race to Dubai as he moved to ten under alongside fellow Australians Nick Flanagan, Geoff Ogilvy and Shae Wools Cobb, Northern Irishman Jonathan Caldwell and Spaniard Alejandro Cañizares.
In the women's event, Swede Madelene Sagstrom led the way at 13 under by one shot from American Ally McDonald.