The world No 2 shuttler won the first game 23-21 and was leading 6-1 in the second game when world No 1 Shi Yu Qi from China retired after showing signs of pain in his right shoulder at the Axiata Arena in Bukit Jalil here.
It was a memorable title for Kunlavut as he is the first Thai player to win the singles crown in 68 years. The last time was in 1958 when Charoen Wattanasin lifted the title.
This was also Kunlavut’s third Super 1000 title in his career.
The Thai won US$101,500 in prize money while Yu Qi took home US$49,300.
The other winners from today’s final day of action at the Malaysia Open are An Se Young of South Korea in the women’s singles, Liu Sheng Shu-Tan Ning (China, women’s doubles) and Feng Yan Zhe-Huang Dong Ping (China, mixed doubles).
Malaysia’s Aaron Chia-Soh Wooi Yik will take on world No 1 pair, Seo Seung Jae-Kim Won Ho from Korea, in the men’s doubles final later.