Today's other Group C tie sees Chinese Taipei take on Tajikistan in a match that will decide third and fourth place.
The Group D activities also are scheduled for today, with Japan challenging Australia in an encounter that will decide which team advances to the quarter-finals as the group table-toppers.
The other match features Qatar and Malaysia. The West Asian side's coach, Tiago De Sousa, has said he is looking for a more positive performance from his players.
Duong Anh Tung and Tran Van Vu each took a double in Vietnam's 8-1 win over Tajikistan.
Tung needed only 23 seconds to push Vietnam ahead at Universal Stadium.
Fayzali Sardorov equalised at the midway stage of the first half for the Central Asia side, but further strikes from Vu and captain Nguyen Bao Quan put the Southeast Asians 3-1 to the good at the interval.
Tung then headed in his second shortly after the restart before Le Quoc Nam, Tran Long Vu, Phung Trong Luan and (Van) Vu wrapped up the scoring.
"It is not an easy game, as our rivals are much bigger than we are. But we strictly follow our tactics and are well combined with each other, so we have really good results," said forward Long Vu.
"I'm really happy with the performance, because we dominated the game," said Formoso.
"It's difficult to play against a team like Tajikistan, because they defend well and play a direct style. But we scored the first goal, so they needed to open up more.
"We were comfortable in the first half and then played really well in the second. We followed our identity and pressed the ball, wanted possession and attacked."
"We scored more goals and became more confident as the game went on," Formoso added.