Vietnamese No 1 seed Ly Hoang Nam lost to Rio Noguchi of Japan 6-7(6), 0-6.
Nam is world No 461, while Rio is world No 923.
Another Vietnamese representative, Trinh Linh Giang was also defeated by No 4 seed Ryota Tanuma of Japan 6-3, 3-6, 5-7. While young talent Nguyen Van Phuong was beaten 4-6, 2-6 against the Republic of Korea's Nam Ji Sung.
Earlier, Nam was the runner-up in the men’s singles category of the F1 Futures tennis tournament. Nam and his senior partner, Le Quoc Khanh, also earned the silver medal in the doubles event.