Wangcharoen had already caused a stir at the Super 1000 World Tour competition at Istora Gelora Bung Karno when he defeated local favourite Anthony Ginting in round two.

He was at his sharpest today as he won in straight sets against China's Huang Yu Xiang in the quarter-finals, the stage at which he bowed out in last year's tournament.

Despite Huang running him close in the second set, the 20-year-old held his nerve in recording a 21-10, 21-17 triumph.

"I’m very excited because this was the quarter-finals," said Wangcharoen.

"I’m really happy with my performance today as I’m in my first major semi-final.”

The Thai had shown glimpses of his talent when reaching the Thailand Masters final two years ago and he was a surprise qualifier at the BWF World Tour Finals in 2018.

He will face Chinese Taipei's Tien Chen Chou in tomorrow's semi-final after the fourth seed overcame Indonesia's Jonatan Christie 16-21 21-18 21-14.

Wong Wi Ki Vincent defeated Hong Kong compatriot Ng Ka Long Angus 21-17, 21-19 to reach the last four.

He will face Zii Jia Lee of Malaysia, who progressed after his quarter-final opponent, Anders Antonsen of Denmark, retired.

In the women's draw top seed Tai Tzu-ying from Chinese Taipei came through a gruelling three-set duel against Ratchanok Intanon of Thailand.

Tai had relinquished her lead in the second set before regaining her composure to see off the seventh seed 21-18, 16-21, 21-12.

In the mixed doubles, top seeds Si Wei Zheng and Ya Qiong Huang of China enjoyed a straight sets 21-12, 21-13 victory against English pair Marcus Ellis and Lauren Smith.

Second seeds Yi Lyu Wang and Dong Ping Huang, also from China, won 21-4, 21-15 against Malaysians Soon Huat Goh and Shevon Jemie Lai.