The world No.8 Singapore shuttler was up in the men's singles quarter-finals against Thailand's world No.17 Kunlavut Vitidsarn - who had defeated him in the SEA Games final back in May - and once again found the defensive specialist a wall too tough to break, as he succumbed 12-21, 21-17, 8-21 in 64 minutes.
"I gave my best, I gave my all, but I couldn't win," Loh told The Straits Times after his loss.
"I have no regrets because I gave everything on the court. (Kunlavut) was more ready for the third game to control the pace, and that's something I need to work on.
"Overall, I have been playing the best I can. I think I did okay, I'm satisfied with my performance, but definitely there's a lot more to improve on."
Despite a mini-revival in the second game where he scored 10 straight points, the 25-year-old Loh rarely looked capable of controlling the match against the 21-year-old Thai, who was a three-time world junior champion from 2017 to 2019.
Nonetheless, he ends his eight-month reign having written a significant slice of Singapore sporting history by becoming the city-state's first badminton world champion.
Kunlavut will go on to meet China's Zhao Junpeng in Saturday's semi-final. Zhao, ranked world No.23, took 64 minutes to subdue India's HS Prannoy 19-21, 21-6, 21-18, a day after stunning Malaysia's world No.5 Lee Zii Jia in the round of 16.
The other semi-final will be contested between Taiwan's world No.4 Chou Tien-chen and Indonesia's Anthony Sinisuka Ginting or Denmark's world No.1 Viktor Axelsen.
Started title defence well with convincing wins
Loh had lost to Kunlavut at the SEA Games gold-medal match, following a gruelling semi-final battle with Vietnamese veteran Nguyen Tien Minh.
He had entered the World Championships still licking his wounds from an early exit in the Commonwealth Games earlier this month. He had been the top seed at Birmingham, but was stunned by Malaysia's Ng Tze Yong in the quarter-finals.
A tough battle was expected against his round-of-16 opponent, world No.11 Angus Ng of Hong Kong, but Loh was at his best form to win the first game 21-11, before an unfortunate injury forced Ng to withdraw while trailing 4-11 in the second.
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