Fresh from winning the India Open on Sunday, Kunlavut Vitidsarn seeks back-to-back titles at this week's Indonesia Masters.
The 21-year-old Thai stunned world No.1 Viktor Axelsen 22-20, 10-21, 21-12 in New Delhi for the biggest win of his career.
It was Kunlavut's first win in seven meetings with the Dane who had not lost in 13 straight finals.
"It's a big result for me, as I'd lost six times to him," said Kunlavut.
"I had no pressure. I couldn't outlast him in the rallies so I attacked a lot more. I tried not to think too much, and kept adapting as the match went on."
Axelsen, whose last defeat in a final was to Lee Zii Jia of Malaysia at the All England in 2021, was gracious in defeat and complimented the winner.
"The last few times against him I came out winner, however today it was different and he deserved the win. I have to keep working hard and hopefully next time I can beat him," Axelsen told bwfbadminton.com.
"I want to congratulate Kunlavut for the win -- he played a great game. My attack and my presence on court wasn't the best and that's something I have to do better next time."
"This is competitive badminton. Even though I've done well in the last many finals, you cannot expect that I keep winning and winning and winning," he added.
"I try to do my best every time, but unfortunately today wasn't my time, it was Kunlavut's time."
The two could meet again in the final this week as they are in opposite halves of the draw. Kunlavut was handed a tough assignment in his opening match in Jakarta as he faces Axelsen's compartiot Anders Antonsen.
Axelsen will begin his campaign in the Super 500 event against China's Lu Guangzu.
Other Thais in the tournament include Ratchanok Intanon and Pornpawee Chochuwong, who takes on top seed Akane Yamaguchi of Japan in the opening round.