The 15-year-old amateur –– fired a seven-under-par 65 to finish on 20-under and beat Korean Joohyung Kim by two shots at Siam Country Club’s Waterside Course.

Kim, aged 19, returned a 64 while American left hander Paul Peterson and Bio Kim from Korea ended third one stroke behind after firing 68 and 69 respectively.

Ratchanon at 15 years old and 37 days old improved upon the previous best youngest winner mark set by Japan’s Ryo Ishikawa, who was 15 years and eight months when won the Japan Tour's 2007 Munsingwear Open KSB Cup.

And on the Asian Tour Thailand’s Chinnarat Phadungsil had been the previous youngest champion, having claimed the 2005 Double A International Open when he was 17 years and five days old.

“I am very excited, but I felt a lot of pressure. I got to be honest, I got pretty lucky, I had hit two or three terrible drives." Ratchanon Chantananuwat.

In one of the most captivating and historic finishes to an Asian Tour event, a whole host of players were in contention on the back nine.

But Ratchanon, playing in the penultimate group, made the decisive move when he birdied 14 and 15, for a three-shot lead over the chasing pack.

His cause was also helped when Kim, playing two groups ahead, found water on 17 and made bogey.

That appeared to hand victory to Ratchanon, but Kim sensationally holed a 15 footer for eagle on the par-five 18th to get to 18-under and give the young Thai golfer a one-shot lead playing the last.

Once again showing maturity beyond his years, Ratchanon split the fairway with his drive, laid up safely short and holed a birdie putt from 12 feet.

“I am very excited, but I felt a lot of pressure,” said Ratchanon.

“I got to be honest, I got pretty lucky, I had hit two or three terrible drives. I saw that [Kim eagled 10] and was not surprised, he pulls off that stuff all the time. It put pressure on me but I tried not to look at it too much. I definitely have a lot of people to thank.”

The rising star, who studies at Shrewsbury International School Bangkok, has no plans to turn professional and will compete in the upcoming SEA Games in Vietnam.

He said: “This has been my plan all along. I enjoy going to college and learning everything. I have talked to a lot of players, and they have all said go to college.”

He also became the fifth amateur to win on the Asian Tour and first since 2009.

Kim, the reigning Asian Tour Order of Merit champion, had the consolation of receiving the US$135,000 winners’ cheque.

“Made a careless mistake on 17 but recovered well with the eagle but let’s face it, TK deserves this. There is no stopping him. But this week has given me a lot of confidence for the season ahead,” said Kim.

Four-time Asian Tour winner John Catlin from the United States returned a 67 to finish in outright fifth, while in a tie for sixth was 17-year-old Chanoknan Angurasaranee from Thailand.

The US$750,000 tournament marked the first time the Asian Tour have staged a mixed event, as it is being jointly sanctioned with the Ladies European Tour (LET).

Competitors move to the Trust Golf Asian Mixed Stableford Challenge next week, to be played at the same venue and boasts the same prizemoney.

The inaugural tournament will use the Modified Stableford scoring format.