The Indian faces another Japanese, fifth seed Akane Yamaguchi, in the last eight.
In the second, she simply stamped her class and never relinquished control to complete the win in just 26 minutes.
On the other hand, World No.6 Ratchanok has never reached the final here, her best performance being the semis in 2015, while Sindhu finished runner-up in the tournament previous year as she lost the summit clash in straight games to Tai Tzu-ying of Chinese Taipei. It is a fine win considering the Japanese was seeded number five.
Sixth seed Ratchanok beat Canadian Michelle Li 21-14, 21-16 in 39 minutes in the other quarter-final.
Talking about some earlier action in the tourney, Sindhu marked her spot in the quarter-finals by coming strong over Aya Ohori of Japan and defeating the Asian junior champion 21-14, 21-17.
In another match, eighth seed Chen Yufei of China edged past Saina 18-21, 21-19, 21-10 in a marathon match which lasted an hour. Also, this will be their first meeting this year. The 23-ranked Japanese got the better of Prannoy for the third time in as many matches. He squandered three match points to slump to a 21-15, 9-21, 20-22 defeat to the World No. 52 Lee Dong Keun of Korea.