Nam, who is unseeded, defeated No 6 seed Daniele Capecchi of Italy 5-7, 7-5, 6-2 in a 2hr 48min match.
It was the third time in a row Nam came from behind to win at the tournament and Capecchi was the second seed eliminated by Nam at the event. The first was No 2 Evgenii Tiurnev of Russia in the first round on February 26.
Nam will next face David Poljak of the Czech Republic. The No 3 seed defeated No 7 seed Oleksii Krutykh of Ukraine 6-2, 5-7, 7-6 (4) on February 28.
