The Indian has struggled after winning the global title for the first time in Basel in August and was knocked out today by Thailand's Busanan Ongbamrungphan.

Sindhu, seeded sixth, went down 21-18, 11-21, 21-16 at Hong Kong Coliseum as the Thai reached the quarter-finals.

Japan's second seed Akane Yamaguchi, the best ranked player left in the women's draw, advanced by beating compatriot Aya Ohori 23-21, 21-13.

China's third seed Chen Yufei needed three games to knock out Japan's Sayaka Takahashi, 21-9, 17-21, 21-10.

Nozomi Okuhara, Japan's 2017 world champion and fourth seed, went through with a 21-16, 21-10 success over Thailand's Pornpawee Chochuwong as she continued her defence of her Hong Kong title.

In the men's draw at the World Tour Super 500 tournament, second seed Chou Tien-chen had to come from behind to go through.

The Chinese Taipei shuttler, who is the top ranked player left in after Japan's back-to-back world champion Kento Momota withdrew, saw off India's Parupalli Kashyap 12-21, 23-21, 21-10.

There was no joy for China's third seed Shi Yuqi, however, who exited the tournament while still battling a toe blister.

He was beaten by Hong Kong qualifier Lee Cheuk Yiu, 21-9, 26-24.

World Championship runner-up Anders Antonsen of Denmark, the fourth seed, was too strong for China's Beijing 2008 and London 2012 Olympic champion Lin Dan, winning 21-14, 21-11.

Reigning Olympic champion Chen Long did make it through as China's Rio 2016 winner bounced back from a poor start to knock out Chinese Taipei's Wang Tzu-wei, 18-21, 21-12, 21-14.

The quarter-finals are tomorrow.