Indonesia started strongly and held the majority of possession for the first 20 minutes with Thailand relying on counter attacks as Supachai Jaided looked dangerous on the ball.
However, the Young Garuda fell behind a minute later after Shinnaphat Leeaoh found the back of the net connecting from Worachit Kanitsribumphen’s free-kick to give Thailand a 1-0 lead at half-time.
Supachai continued to cause problems for Indonesia in the second half and earned a penalty nine minutes after the restart.
The Buriram United forward made no mistake from the spot, beating goalkeeper Awan Setho to double Thailand’s advantage.
Indra Sjafri brought in fresh legs with Sani Riski Fauzi replacing Saddil Ramdani in the 51st minute and Witan Sulaeman coming on for Osvaldo Haay 12 minutes later, but there was no stopping Thailand.
In a swift attacking move from midfield, the young War Elephants advanced on their opponents and Supachai finished cooly in the 71st minute after connecting to a cross from the right.
There was no respite for Indonesia as they conceded a fourth three minutes later when Supachok Sarachat wriggled his way into the box before scoring a clinical finish.
Next up for Thailand is a match against Brunei on Sunday, while Indonesia will take on 2018 runners-up Vietnam.