Fifth seed Prannoy, who finished runners-up at the $50,000 Vietnam Grand Prix in Hochiminh City last week, edged out Liew, seeded ninth, 21-14, 14-21, 21-14 in a close to an hour semi-final clash.
The Indian will take on the winner of the other semi-final between qualifier Firman Abdul Kholik of Indonesia and Malaysia's Zulfadli Zulkiffli in the final on Sunday.
The 22-year-old Prannoy, who had beaten Liew, a former top 10 player, during their only encounter at the 2012 Malaysia Open GP Gold, fought back from 5-8 down to eventually break off at 12-12 to earn the bragging rights.
In the second game, Liew turned the tables on the Indian as he opened up a 7-3 lead early on and even though Prannoy reduced the gap to 8-9, the Malaysian didn't allow him to come any closer after that to bounce back into contest.
Jolted by the second game loss, Prannoy zoomed ahead 5-0 in the decider and entered the break with a slight edge at 11-9. The Indian held on to his nerves after that even as Liew crumbled under pressure.
Prannoy won a silver medal in Boys' singles at 2010 Summer Youth Olympics.
Image: HS Prannoy
Photograph: Robertus Pudyanto/Getty Images
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