ABERDEEN, 2 Aug 2015, (AFP) - The 26-year-old Thai, already a two-time tour winner after capturing the 2013 Malaysia Open and this year's Shenzhen International, was three up with four holes to play.
However, the Swede hit back on the 15th, 16th and 17th to set-up a dramatic last hole duel.
Kiradech held his nerve on the 18th where he putted from four feet just after Karlsson had dragged his birdie attempt wide.
"My next step was to win in Europe, so I am happy and so proud of myself," said Kiradech, whose burly frame has led him to be dubbed "Asia's John Daly" in honour of the big-hitting, two-time major winner from the United States.
"I was striking the ball well and hitting it so good on the front nine, but then I lost a bit of energy and control.
"I started pulling some drives but I have to say I putted very well today and sank a lot of important putts – especially the putt to win which was very short but it was great to see it hit the middle of the hole.
"I didn’t have too high expectations this week but I just came here and tried to enjoy the whole experience of playing in Scotland."
Kiradech, who ended hopes of a home win when he saw off Scotland's Marc Warren in the last four, took a two hole lead in the final with birdies on three of the first four holes.
That advantage increased at the sixth as Karlsson twice tangled with the heavy rough.
Karlsson reduced the deficit to just one hole after firing birdies at the eighth and ninth but his Thai rival took the 11th and 14th to return to three up.
Despite the defeat, Karlsson was pleased with his display.
"It was much better than I expected coming in here. I can take a lot of positives out of it," he said.
David Howell recovered from his narrow semi-final defeat to Karlsson to beat Warren by one hole in the third-place play-off.
Final day scores in the Paul Lawrie Matchplay EPGA tournament at Murcar Links Golf Club, Aberdeen, Scotland on Sunday (GBR/IRL unless stated):
Final
Kiradech Aphibarnrat (THA) bt Robert Karlsson (SWE) 1 up
3rd place play-off
David Howell bt Marc Warren 1 up