The ex-world number one and 2013 world title-holder beat the unseeded Chen 21-17, 21-15 to set up an all-Thai clash with Pornpawee Chochuwong, who beat Hong Kong's Cheung Ngan-yi.

In a much-depleted men's draw, Taiwanese third seed Chou Tien-chen advanced with a comfortable 21-12, 21-16 victory over Kenta Nishimoto of Japan.

With the world championships in Basel looming later this month, Kento Momota of Japan and China's Shi Yuqi, the world number one and two, both withdrew, while Chinese greats Chen Long and Lin Dan were early casualties.

Third seed Chou, 29, will play unseeded Lee Zii Jia from Malaysia, while defending champion Kanta Tsuneyama faces Hong Kong's Angus Ng or Khosit Phetpradab of Thailand.

The women's tournament has also been hit by withdrawals after last year's winner Nozomi Okuhara, world number one Akane Yamaguchi and Olympic silver medallist PV Sindhu all pulled out.

Top seed Chen Yufei cruised into a semi-final against Japan's Sayaka Takahashi with a convincing straight-games win over Soniia Cheah of Malaysia.