Third seed Antonsen, who had won the last meeting between the two at the Thomas Cup, got the better of the defending champion again, prevailing 9-21, 24-22, 21-18 in one hour and 37 minutes.
Kunlavut, who also won the tournament in 2023, had hoped to become the first men’s singles player since Joko Suprianto in 1994 to win three titles, reports the Bangkok Post.
Antonsen took home his first title of the year along with the US$37,500 (B1,237,500) winner’s cheque. Kunlavut received $19,000.
Earlier, Akane Yamaguchi was crowned a new women’s singles champion of the Thailand Open after she dethroned Chen Yufei 21-14, 21-18.
The Japanese took 39 minutes to defeat Chen, who had hoped to become the first Chinese women’s singles player in 19 years to retain her title after Zhu Lin in 2007.
Unseeded Leo Rolly Carnando and Daniel Marthin of Indonesia won the men’s doubles crown after they upset top seeds Satwiksairaj Rankireddy and Chirag Shetty of India 21-12, 25-23.
It was an impressive comeback by Marthin, who returned to the circuit after missing a year due to injury and reunited with his former partner Carnando at the Bangkok tournament.
The Indonesian duo split in mid-2024, with Marthin partnering Muhammad Shohibul Fikri and Carnando paired with Bagas Maulana. At the Sudirman Cup Finals last May, Marthin suffered a left knee cartilage injury and needed surgery, with the layoff ending only with the Thailand Open.
There was another upset in the women’s doubles decider, with unseeded Bao Lijing and Cao Zihan of China edging top seeds Rin Iwanaga and Kie Nakanishi of Japan 19-21, 21-16, 21-19.
Mathias Christiansen and Alexandra Boje, who made their third straight final, defeated China’s Zhu Yijun and Li Qian 21-17, 21-15 in the mixed doubles decider. Zhu and Li upset Thai top seeds Dechapol Puavaranukroh and Supissara Paewsampran in the semi-finals.