Thailand led Myanmar by one goal at halftime, with the forward scoring in the 23rd minute before doubling it with a penalty kick eight minutes into the second half, reports the Bangkok Post.
Worachit Kanitsribampen and Supachok Sarachat also put the ball into the net in the second game for the War Elephants at the National Stadium in Singapore.
“We learned from the mistakes made in the first match,” Teerasil said after the game.
Thailand began their Group A campaign with an unconvincing 2-0 win over Timor Leste on Dec 5.
Myanmar have played three games in the Singapore tournament with two losses against Thailand and Singapore, and one win over Timor Leste.
Thailand will meet the Philippines on Tuesday and Singapore next Saturday.
Defending champions Vietnam are in Group B with Malaysia, Indonesia, Laos and Cambodia.
The top two teams in each group reach the semi-finals with the final scheduled for Jan 1.
The 2020 edition of the biennial Asean championship was postponed from last year due to the COVID-19 pandemic.