LONDON, June 2, 2012 (AFP) - Jaidee, a three-time Asian number one, started and finished with birdies to complete a solid four-under-par 67, which gave him a one-shot lead over England's Ross Fisher and Dutchman Joos Luiten.
Jaidee, ranked 199th in the world to Fisher's 157th, birdied the par-five last after an incredible drive measured at 410 yards.
"I think 320 is the longest for me, so when we got to the top of the hill I asked, 'Where's the ball?' and a marshall told me," he said.
"I thought it was 390, but 410 sounds better."
The 42-year-old Jaidee has won four European Tour events in total, but all of those events were played in Asia.
"I've won a lot of times in Asia and I've played well a lot of times in Asia," added Jaidee.
"In Europe, it's very important for me to do well because the weather is going to be very difficult for me. I've learned a lot of things -- how to play with these conditions.
"I think this time it's a very good chance. You never know how it's going to be tomorrow (Sunday), but I'll try to give it my best and look forward."
Fisher had reignited his dream of playing in the Ryder Cup by taking the lead at the halfway stage on Friday with a five-under-par 66.
But the accident-prone Englishman had to overcome another incident -- stubbing his toe in his hotel room on Friday night -- to keep himself in contention with a level-par 70 that was marked by five birdies but also five bogeys.
"There were a few expletives and it was extremely painful," said Fisher. "I couldn't put any weight on it and half-contemplated playing in trainers.
"One of the toes is as purple as anything. I iced it and two of the toes were strapped together, but I hit it everywhere and I'm glad to finish."
Fisher has dropped 130 places on the rankings since he helped Europe to victory in the Ryder Cup two years ago, at Celtic Manor.
It places special significance on victory on Sunday.
"It would mean a lot to win. I set very high standards and I reached 17th in the world, so I know I have the game," said Fisher.
"Given where I hit it, that's one of the best level-par rounds I've ever had. I hung in there and dug deep.
"The 63 I had at the European Open (an event he won by seven shots at The London Club in 2008) was good, but today was impressive."
Luiten started the day in a tie for 20th and was even deeper in the pack after a bogey on the fifth.
But birdies at the next two holes sparked a recovery and by the time he sank a 25-foot putt for an eagle two at the 15th, he was out in front.
After two-putting the last for his sixth birdie he said: "It hasn't been a great season, but it's a course that if you play well, you can shoot a decent score."
Collated third round scores in the European Tour Wales Open at Celtic Manor (GBR and IRL unless stated, par 71):
206 Thongchai Jaidee (THA) 71 68 67
207 Ross Fisher 70 66 71, Joost Luiten (NED) 74 69 64
208 Tim Sluiter (NED) 68 72 68
209 Carlos Del Moral (ESP) 75 68 66, Marcel Siem (GER) 68 75 66
210 Richard McEvoy 71 70 69, Mark Foster 72 69 69, George Coetzee (RSA) 71 71 68
211 Damien McGrane 71 71 69, Thomas Bjorn (DEN) 71 72 68, Gregory Bourdy (FRA) 74 69 68, David Lynn 73 71 67, Richard Sterne (RSA) 73 69 69
212 Thorbjorn Olesen (DEN) 73 68 71, Matteo Manassero (ITA) 76 68 68, Jaco Van Zyl (RSA) 72 69 71, Gonzalo Fdez-Castano (ESP) 69 74 69
213 Emiliano Grillo (ARG) 73 69 71, Chris Wood 72 67 74, Joel Sjoholm (SWE) 69 74 70, Romain Wattel (FRA) 73 72 68, Keith Horne (RSA) 79 66 68, Lorenzo Gagli (ITA) 77 70 66, Raphael Jacquelin (FRA) 76 65 72
214 Magnus A Carlsson (SWE) 77 67 70, Robert Coles 73 69 72, Peter Lawrie 72 73 69, Lee Slattery 67 71 76, Pablo Larrazabal (ESP) 69 74 71, Oscar Floren (SWE) 78 69 67, Brett Rumford (AUS) 74 70 70, David Drysdale 72 71 71, Federico Colombo (ITA) 79 68 67, Paul Lawrie 74 69 71, Fabrizio Zanotti (PAR) 70 69 75
215 George Murray 75 71 69, Matthew Zions (AUS) 76 71 68, Steven O'Hara 70 72 73, Paul McGinley 72 73 70
216 Francesco Molinari (ITA) 74 69 73, Scott Hend (AUS) 80 66 70
Selected:
218 Jean-Baptiste Gonnet (FRA) 74 69 75, Colin Montgomerie 74 72 72, Marcus Fraser (AUS) 70 77 71, Gregory Havret (FRA) 75 72 71