KAVARNA, Bulgaria, May 16, 2013 (AFP) - Thongchai fought back from being 2 down earlier in his match against last year's European Ryder Cup winning star to claim the match 3 & 2 with a birdie at the 16th hole on the spectacular Thracian Cliffs course.
"It was a very solid day for me today after the start where I lost a couple of holes with poor concentration," said the Thai.
"I had played well in the Pro-Am but then I was very worried when Ian birdied the first three holes. However, then I played a very solid round of golf and I am very happy with that.
"I will continue to try my best now and try to continue with my good driving on a very tricky golf course."
Poulter, who had raced to 2up after three holes, had complained of stomach cramps on the course but refused to dwell on any illness after putting a ball over the cliff top at the fourth hole and then taking a double bogey on 14 before losing the match on 16 to a Thongchai birdie.
"I'm feeling alright," he said when asked about any illness.
"I made a few mistakes and just handed too many holes to Thongchai. So all in all, he played well enough to beat me today, which was good enough.
"I've played Thongchai enough, he's a great player. I gave him holes today and you don't do that in match play, dead simple.
"This is the type of course where if you hit a couple of errant shots, you're going to be struggling to be back in the hole, simple."
In the other shock on day one of the three million euro event, defending champion Nicolas Colsaerts was beaten 4 & 3 by South African Branden Grace.
"I didn't think I played that good and that's just pure and simple," said Colsaerts.
"I missed a couple of putts that had I holed would have made my day a lot easier and bring myself into the match.
"So when you miss those putts the gap between Branden and myself just got bigger and bigger."
Northern Ireland's Graeme McDowell, and the highest world ranked player in the field at number eight, also recorded the biggest victory in defeating England's Chris Wood 5 & 3.
McDowell, who lost to Colsaerts in last year's final, was 3up after eight holes and while he lost the 12th to the current Qatar Masters champion, he closed the match winning the 13th, 14th and 15th holes.
"To get this win under the belt today is very important as it really eases the pressure off me going into tomorrow," said McDowell.
Opening round matches at the Volvo World Match Play Championship, Thracian Cliffs Golf & Beach Club, Kavarna, Bulgaria on Thursday:
Gonzalo Fernandez-Castano (ESP) bt Jamie Donaldson (WAL) 1 up
Carl Pettersson (SWE) bt Thorbjorn Olesen (DEN) 4 & 3
Francesco Molinari (ITA) bt Henrik Stenson (SWE) 2 & 1
Branden Grace (RSA) bt Nicolas Colsaerts (BEL) 4 & 3
Bo Van Pelt (USA) and Richard Sterne (RSA) match halved
Peter Hanson (SWE) bt George Coetzee (RSA) 2 & 1
Thongchai Jaidee (THA) bt Ian Poulter (ENG) 3 & 2
Graeme McDowell (NIR) bt Chris Wood (ENG) 5 & 3