Vien triumphed in the women’s 200m backstroke, clocking 2:15.32, followed by swimmers of Indonesia and the hosts Philippines.
This is the fourth consecutive time the Can Tho-born swimmer has brought home a gold medal in this category.
She earned a gold medal in the 200m freestyle earlier the same day and another in the 200m individual medley on December 4.
Vietnam won a total of seven gold, six silver and 11 bronze medals on December 6. However, these achievements could not help the country retain its second place on the medal tally as it dropped to the third position with 131 medals, including 38 golds, 41 silvers and 52 bronzes.
The Philippines maintained its top spot with 176 medals, including 71 golds, 55 silvers and 50 bronzes.
Indonesia came second with 128 medals, comprising 40 golds, 41 silvers and 47 bronzes.