Nam easily trounced Japanese Ken Oshini 6-1, 6-3 in a 70-minute match.
Wild card Nguyen Hoang Thien was eliminated from the tournament after a 1-2 loss to Masato Shiga of Japan on October 19.
Thiên played equally to the No 3 seed in the first two sets, which ended 5-7 and 7-5, as both players lost a break point in the last games.
However the Vietnamese could not maintain the high peak in the third set. He quickly collapsed and was defeated 2-6.
Shiga advances to the quarter-finals where he will play host representative Nam.
In other matches, No 2 Laurent Rochette of France beat Sam Matheson of New Zealand 6-2, 6-3; Australian Stefan Skadarka came from behind to beat Mislav Bosnjak 3-6, 6-1, 7-6 (5); No 8 seed Noh Sang-woo of the Republic of Korea won 6-2, 5-7, 6-1 over Jirat Navasirisomboon of Thailand.