Le Thi Bang lost to Indian rival Hmangte 0-3 in female under-51kg category.
Luu Thi Duyen was defeated by Chinese competitor Yin Junhua 0-3 in female under-60kg category.
Taekwondo artists Tam and Cuong were beaten by two other foreign competitors with a score of 0-6 and 1-14, respectively.
Only taekwondo artist Nguyen Thanh Thao passed the qualifying round and earned a berth to the quarter-final. However, Thao was defeated by Taiwanese rival Huang Yun Wen 5-13 in the quarter-final on the same day.
In the medal tally, Vietnam, with 32 medals, ranks 20th overall out of 33 participating countries.
What the stars mean:
★ Poor ★ ★ Promising ★★★ Good ★★★★ Very good ★★★★★ Exceptional