CELTIC MANOR, Wales, June 3, 2012 (AFP) - Jaidee shot a one-over par 72 in the final round to win by a stroke from Spain's Gonzalo Fernandez-Castano, who leapfrogged his way up the leaderboard with a four-under par 67, South Africa's Richard Sterne, Danish veteran Thomas Bjorn, and the Netherlands' Joost Luiten.
This was 42-year-old former paratrooper Jaidee's fifth win on the tour but first in Europe.
He led by one overnight, but fell one behind after a double-bogey seven at the ninth hole.
Jaidee didn't manage a single birdie on the outward nine holes Sunday but from the turn he struck three in a row.
That gave the world number 199 some breathing space and meant he could bogey the 16th and the last and still take the £300,000 ($461,000) winner's cheque with an aggregate score of 278 -- six-under par for the tournament.
"I want to say thank-you to all my family, all the supporters and the sponsors here," said a delighted Jaidee. "Conditions were quite tough for me.
"I tried to hit everything on the fairway -- that's the main thing -- then hit the ball on the green. It was very, very tough for me, not like Thailand."
However, there was controversy on the back nine when England's Ross Fisher was penalised a shot for slow play when just one off the lead.
Fisher was deemed to have fallen foul of European Tour rules when he took too long over shots at the 11th and 14th holes and he subsequently fell back to finish in joint sixth on a course where he represented Europe in the Ryder Cup two years ago.
Although by no means unheard of, it is rare for a player who is contending for the title to be penalised in such a way on the final day of a professional tournament on one of golf's main tours.
"I don't think it's justice, but there you go," said Fisher, who was fined £6,000.
However, tour chief referee John Paramor, who gave Fisher, Jaidee and Luiten a warning regarding slow play as early as the sixth hole, was confident he'd made the correct decision after Fisher took 57 seconds over a shot on the 11th having been given 40 by the experienced rules official.
"It was a clear bad time," said Paramor. "Then on the 14th green he took 55 seconds over his first putt.
"I told him before he teed off at the 15th -- and I don't think he was particularly happy."
During the 2009 British Open at Turnberry in Scotland -- where Fisher led early in the final round -- Paramor, concerned by the Englishman's pace of play, gave him a video to study after the end of the championship.
"I think he struggles," said Paramor. "His pre-shot routine is not quick. Today was clearly very important to him -- he was contending -- and he was extending his routine by a whisker."
Bjorn and Fernandez-Castano both boosted their hopes of representing Europe against the United States at this year's Ryder Cup at the Medinah Club near Chicago in September.
But the round of the day belonged to Ireland's Paul McGinley, a Ryder Cup vice-captain two years, who shot a 65.
Collated fourth round scores in the European Tour Wales Open at Celtic Manor on Sunday (GBR and IRL unless stated, par 71):
278 - Thongchai Jaidee (THA) 71-68-67-72
279 - Joost Luiten (NED) 74-69-64-72, Thomas Bjorn (DEN) 71-72-68-68, Gonzalo Fdez-Castano (ESP) 69-74-69-67, Richard Sterne (RSA) 73-69-69-68
280 - Ross Fisher 70-66-71-73, Paul McGinley 72-73-70-65
281 - Joel Sjoholm (SWE) 69-74-70-68, Romain Wattel (FRA) 73-72-68-68, Peter Lawrie 72-73-69-67
283 - Carlos Del Moral (ESP) 75-68-66-74, David Drysdale 72-71-71-69, David Lynn 73-71-67-72
284 - Chris Wood 72-67-74-71, Paul Lawrie 74-69-71-70, Gregory Bourdy (FRA) 74-69-68-73, George Coetzee (RSA) 71-71-68-74
285 - Magnus A Carlsson (SWE) 77-67-70-71, Robert Coles 73-69-72-71, Richard McEvoy 71-70-69-75, Jaco Van Zyl (RSA) 72-69-71-73, Raphael Jacquelin (FRA) 76-65-72-72, Brett Rumford (AUS) 74-70-70-71, Federico Colombo (ITA) 79-68-67-71, Thorbjorn Olesen (DEN) 73-68-71-73, Tim Sluiter (NED) 68-72-68-77, Mark Foster 72-69-69-75
286 - Damien McGrane 71-71-69-75, Matteo Manassero (ITA) 76-68-68-74, Fabrizio Zanotti (PAR) 70-69-75-72, Pablo Larrazabal (ESP) 69-74-71-72, Lee Slattery 67-71-76-72
287 - Jean-Baptiste Gonnet (FRA) 74-69-75-69, Marcel Siem (GER) 68-75-66-78
288 - Emiliano Grillo (ARG) 73-69-71-75, George Murray 75-71-69-73, Tom Lewis 74-71-72-71, Keith Horne (RSA) 79-66-68-75, Matthew Zions (AUS) 76-71-68-73, Joakim Lagergren (SWE) 72-72-74-70, Simon Thornton 69-73-77-69
289 - Stephen Gallacher 77-70-75-67, Knut Borsheim (NOR) 74-71-76-68, Oscar Floren (SWE) 78-69-67-75, Marcus Fraser (AUS) 70-77-71-71
290 - Francesco Molinari (ITA) 74-69-73-74, Oliver Fisher 76-71-73-70
291 - Andrew Johnston 75-72-71-73, David Howell 73-69-75-74, Oliver Wilson 73-73-74-71, David Horsey 71-73-74-73, Maarten Lafeber (NED) 74-72-72-73, Steven O'Hara 70-72-73-76, Simon Khan 75-70-74-72, Rich Beem (USA) 77-68-73-73, Reinier Saxton (NED) 74-71-75-71
292 - Jamie Elson 71-75-73-73, Miguel Angel Jimenez (ESP) 76-71-74-71, Tommy Fleetwood 75-68-78-71, Lorenzo Gagli (ITA) 77-70-66-79, James Morrison 77-70-72-73
293 - Ricardo Gonzalez (ARG) 73-72-76-72, Colin Montgomerie 74-72-72-75, Andrew Marshall 72-74-75-72
294 - Gregory Havret (FRA) 75-72-71-76
295 - Benjamin Hebert (FRA) 73-72-75-75
296 - Daniel Denison 78-67-75-76, Steen Tinning (DEN) 73-73-73-77
297 - Graeme Storm 80-67-80-70
298 - Niclas Fasth (SWE) 74-73-70-81, Fredrik Andersson Hed (SWE) 71-75-79-73
299 - Andrea Pavan (ITA) 76-71-74-78
302 - Jamie Moul 78-67-77-80
303 - Scott Hend (AUS) 80-66-70-87