Lam Thuan opened the scoring in the 28th minute with an easy tap to an empty net. Substitute Nguyen Tien Linh made it 2-0 with a sharp finish from inside the box in the final minute of the match.
Viet Nam were made to work by their rivals, who are considered the weakest team in the group.
East Timor also created several threatening chances, including a shot from Walter Gama that hit the bar on the 60 minute mark.
Coach Hoang Anh Tuan was dissatisfied with the win.
"There were some problems that concerned me, such as the teams inability to link up and finish chances," Tuan said.
"We knew the young players would be nervous in the first match of the tournament, and I think that's why they played below par. East Timor were able to trouble us more than we expected.
"However I loved their playing style and the defence was solid. I'm really happy with three points from the first match."
Tuan put his trust in midfielder Thuan, who was replaced nearly 20 minutes after the break.
"He opened the scoring, missed some chances and provided good service for his teammates, but he wasn't at the top of his game. I hope he will play better in the next match."
Viet Nam top the table with a better goal difference than Malaysia and Myanmar.
In their next match tomorrow, Viet Nam will face second-placed Malaysia.
Tuan said Malaysia had a lot of skilled players, but were not a particularly strong team.
In their previous match against East Timor, Malaysian players got cramp after 70 minutes.
However the coach said Viet Nam needed to be careful because both sides had a chance of winning.
