Top seed Prannoy ended the run of local shuttler Niluka Karunaratne, seeded ninth, with a 21-16 19-21 21-9 in men's singles round three.
The 21-year-old, a silver medallist in boys' singles at 2010 Summer Youth Olympics, will next take on compatriot Anup Sridhar, who defeated fifth seed Lucas Corvee of France 21-23 21-17 21-13 in another match.
Second seed Anand Pawar entered the quarters after beating Thai qualifier Mek Narongrit 21-14 21-9, while Aditya Prakash also reached the last eight with an easy 21-15 21-9 win over 10th seed Thomas Rouxel of France at the Sugathadasa Indoor Sports Complex.
She will next take on sixth seeded Thai Supanida Katethong in the semis of the USD 15,000 event.
Fourth seeds Pradnya Gadre and Siki Reddy N reached the semifinals of the women's doubles competition with a 21-18 21-17 win over Thailand's Karnjanavadee Bunsomboon and Rawimon Iamratanamaetheekul.