Thitkul, age 14 years, four months and 19 days, shot a final-round 72 at Phoenix Golf & Country Club in Pattaya, Thailand to take the title by two strokes with a five-under 283 total.
A Thai teenager became the youngest known victor of a professional golf tournament on Sunday, overcoming huge pressure to secure a two-shot victory at the Ladies European Thailand Championship in Pattaya.
Ko held the record on the Ladies European Tour, having won the 2013 New Zealand Open aged 15 years, nine months and 17 days.
In her first appearance on the Tour, Thitikul finished on five-under for the tournament after a level-par fourth round, two shots clear of second-placed Ana Menendez. "I give this win to all Thais", said Atthaya, who said she was inspired by Thai star Ariya Jutanugarn.
However, as the promising teenager is still an amateur, the prize money of €45,000 went to Menendez. Amy Boulden of Wales is two strokes further back in joint third place after a 67: the lowest round of the tournament with Pimpadsorn Sangkagaro of Thailand and Swedish rookie Frida Gustafsson Spang.
Atthaya had previously demonstrated her enormous potential when she finished tied for 37th in the recent Honda LPGA Thailand event, which she played in just a few days after her 14th birthday, on Feb 20. Her aim was to make the cut, gain experience and have fun.
"I'm so happy and proud of myself".
"I was nervous at the first tee", Atthaya said. I just focused on my shots and only on my caddie. But the Mexican player dropped four shots on the front nine, handing Atthaya a two-shot lead at the turn after one birdie and two bogeys on her first nine holes.
"My family do not play golf".