South Korea’s seventh-seeded An Se-young bested Thai star Ratchanok Intanon Friday, halting the former world champion’s progress to the semi-finals of badminton’s Thailand Open after a 22-20, 21-12 game.

The fourth-seeded athlete was no match for the 18-year-old, who prevailed in the first match after a nail-biting 40-shot rally.

“Every shot was incredible and she won on her own game,” said 25-year-old Ratchanok, who noted her opponent had more speed than when they had played before.

The South Korean teen prodigy, who in 2019 was named Most Promising Player, will face Spain’s Carolina Marin, an Olympic and World champion who snatched victory from Thai player Supanida Katethong 21-16, 21-16.

Meanwhile, men’s badminton world number two Chou Tien-chen marched into the semi-finals, coming from behind to beat younger opponent Lee Zii Jia 21-17, 21-15.

Second-seeded Chou will meet eighth ranked Angus Ng, ranked eighth in the world in the semis. Ng handily beat Hong Kong teammate Lee Cheuk-yiu 21-17, 21-12.

Denmark’s Viktor Axelsen also sailed through his game against Indonesian Jonatan Christie.

Axelsen, the fourth seed, will face another Indonesian, sixth-ranked Anthony Ginting.

The Thailand Open is the first of three consecutive tournaments in Bangkok culminating in the World Tour Finals from January 27.

The athletes – flown in a week before the start for quarantine and testing – are competing behind closed doors as a virus precaution.

On Wednesday, a German coach in the tournament tested positive for the virus but his players were allowed to continue competing.

The test result however prompted Hong Kong mixed doubles players Tse Ying-suet and Tang Chun-man to pull out of their next match against the German team.

The Badminton World Federation said they respected the Hong Kong’s team decision but defended allowing the Germans continue, saying all players had tested negative.