The Vietnamese player was defeated 1-6, 4-6 by Son Ji-hoon of the Republic of Korea, a player that Nam has beaten previously.
Nam on May 14 reached his highest world ranking of No 433 while his rival placed 845th in the world.
At the F2 event last week, Nam was also sent out from the second round by 19-year-old Rio Noguchi of Japan who went on to secure the title.
Another Vietnamese player, Nguyen Van Phuong, was also ousted on May 15, losing 4-6, 2-6 to Japanese Gengo Kikuchi.
No 3 seed Jeremy Beale of Australia was sent home early after his 5-7, 2-6 defeat to Rio Noguchi of Japan.
Other top seeds including No 5 Yu Cheng-Yu of Chinese Taipei and No 6 Ryota Tanuma of Japan advanced to the next round.
After Nam’s and Phuong’s exit, Vietnam have only Trinh Linh Giang as a representative in the singles event. He will play the second round against No 2 Karunuday Singh of India on May 16.
Another Vietnamese is Nguyen Bui Tri who is paired with Jayden Court from Australia in the doubles class. They will meet Kittirat Kerdlaphee and Palaphoom Kovapitukted of Thailand in the second round.