The Scot carded a faultless six-under 66 to join Rafael Cabrera-Bello and Richard Green at the top of the leaderboard, while Oliver Farr appeared destined to claim the outright lead until making his only mistake of the round at the 18th.
Cabrera-Bello was first into the clubhouse on six under after he mixed five birdies with a pair of bogeys in his second straight 69, and Australian veteran Green soon matched the Spaniard following a solid, three-birdie 70.
But Ramsay was the biggest mover of the second round, vaulting 51 places up the leaderboard as he birdied five of his first eight holes and added another at the first before parring his final eight holes.
“The last few months have been frustrating,” Ramsay told the European Tour website. “You just want to go out and play. I???ve had a few niggling injuries. I???ve just tried to stick to my guns and make sure I stretch and have a good practice routine.
“That builds up and slowly but surely it comes around and today was the day it happened. Hopefully it can stay for the weekend.”
Wales professional Farr, playing in the final group of the day, suddenly leapt into contention as he followed seven opening pars with a sparkling run of four birdies in six holes around the turn.
The 27-year-old picked up another shot at the long 17th to move into the outright lead, but he bogeyed the 18th for the second day running to return a 68.
The leading quartet are one shot clear of English trio Richard Bland, Ben Evans and Chris Wood, who started with a seven at the 10th before recovering to post an erratic 72 which featured an eagle at 17, two birdies and a pair of bogeys.
Pablo Larrazabal also got to five under after he birdied his final two holes, while George Coetzee kept his hopes of qualifying for the Masters alive despite stuttering to a 72.
The South African, who needs a win to earn a trip to Augusta, recovered from a shaky start with four birdies in five holes from the sixth, but he bogeyed 14, 15 and 18 around another birdie at the 16th.
David Howell posted a second straight 70 to move to four under while Tommy Fleetwood, who can also qualify for the Masters with a win the the Golf du Palais Royal, will go into the weekend just three shots off the lead after signing for a one-under 71.
Fleetwood is alongside fellow Englishman and 2011 champion David Horsey, who took the gloss off a good day’s work with bogeys at the final two holes in his 71, but overnight leader Adrien Saddier slumped to two under after following up his opening 65 with a wayward 77.
Marcel Siem, the 2013 winner, crashed out after a horrific 79 featuring three double-bogeys at par-threes, while defending champion Alejandro Canizares also missed the cut on six over par.
Also having a weekend off is Andy Sullivan, whose Masters dreams ended with a dreadful quintuple-bogey nine at the fourth – his 13th – in a disappointing 75.