Taking part in two events, Vien easily showed her domination and pocketed two records and two titles.
It is her seventh record and ninth gold medal in Singapore.
Hermale teammate, Lam Quang Nhat also picked up his first gold medal herein the 1,500m freestyle event. Nhat, the SEA Games defending champion,clocked 15min 48.26sec. Prawira A Fadlan of Indonesia and Teo Zhen Renof the hosts came second and third, respectively.
The men's 400m medley team later pocketed a bronze medal and finished behind Indonesia and Singapore.
Thehosts began the day with two victories in the women's 50m freestyle and50m breaststroke events, in which Amanda Lim and Lionel Khoo made onerecord each with a time of 25.74sec and 28.93sec, respectively.
However,Vien made it a day for the Vietnam team, as she finished the women's200m backstroke with a time of 2min 12.74sec, beating her own record of2:13.84 set up in 2012.
Later, the Olympian shone in the 200mindividual medley, clocking 2:14.58, which was much quicker than whatshe recorded (2:17.67) two years ago.
On June 21, Hoang Quy Phuoctook his second gold here after winning the men's 100m freestyle eventwith a time of 50.06sec. His result is also a new record, eclipsing theold one of 50.66sec by Danny Yeo Kai Quan of the hosts.
Later,Vien set her fifth record here in the 800m freestyle event. The17-year-old picked up her seventh gold medal after finishing with a timeof 8:40.75, nearly 12sec faster than the Malaysian Khoo Cai Lin's8:52.45 years ago.
Vietnamese swimmers also earned a bronze medalin the men's 200m backstroke, when Tran Duy Khoi finished third behindRicky Anggawijaya and Gede Sidman Sudartawa, both of Indonesia.
TheCan Tho province-born girl became the best athlete of the tournament.Her achievement played a key role in helping Vietnam, with a tally of 12golds, replace Singapore (11) at the top of the overall ranking table.Singapore had dominated the position from the first day on June 17.Thailand were at third, grabbing eight titles.-VNA