Malaysia opened the 2018 AFF Suzuki Cup with a 1-0 victory over Cambodia in Group A on Thursday.
Norshahrul Idlan Talaha scored the only goal 30 minutes into the game when he headed home from eight yards after Syamer Kutty Abba's driving run through midfield eventually allowed Zaquan Adha to send in a decisive cross.
In the group's other game, Vietnam cruised to a 3-0 win over Laos to lay down an early marker for the tournament.
Park Hang-seo's side, who won the regional title in 2008 and are one of the pretournament favourites, were dominant against a Laos team that packed the defence and offered little in the attacking third.
Nguyen Cong Phuong put the visitors in front at the New Laos National Stadium in Vientiane 11 minutes into the game when he rifled a right-foot shot into the top corner from 12 metres out.
And, as the half-time whistle approached, Nguyen Anh Duc scored the second after Luong Xuan Truong's initial effort from distance had come back off the post.
Nguyen Quang Hai's curling free kick found the bottom corner of Saymanolinh Paseuth's goal midway through the second half as the Vietnamese ensured they would top Group A after the opening round of matches.
Malaysia face Laos on Monday while Myanmar take on Cambodia. Vietnam's next game is against the Malaysians on Nov. 16 in Hanoi.
Thailand will begin the defence of the title they have won twice in succession when they face East Timor in Group B on Friday, while Singapore host 2016 runners-up Indonesia.