Hosts Indonesia claimed their second Asean U19 Boys' Championship crown after edging Thailand 1-0 in the final at the Gelora Bung Tomo Stadium in Surabaya on Monday night.
Playing in front of more than 40,000 fans, the home team scored the only goal of the game in the 18th minute through Jens Raven.
Emerson Pereira rued a lapse on the part of the Thai defenders after the loss.
"We made an error, conceded the goal and, in the end, it proved costly," said the Brazilian coach.
"The players are dejected but we can be proud of our performance here -- we made it to the final of the tournament."
The start to the final was sluggish, but it sprang to life when Thailand's Thanawut Phochai hit the post after finding himself one-to-one with the Indonesian goalkeeper in the 15th minute.
The home team were quick to respond as a corner kick fell just in the right spot for Raven to strike home from close range.
After conceding the goal, the Thais started mounting pressure on their opponents and Piyawat Petra missed a clear scoring opportunity, hitting the post from point-blank range in the 37th minute.
The Thais dominated the second half but were denied the equaliser when a Jirapol Saelio shot was warded off by an Indonesian defender 10 minutes from time.
Earlier in the day, Australia took the third place in the competition this year after beating Malaysia 5-3 in a penalty shoot-out following a 1-1 tie at time. Ikran Algiffari from Indonesia was selected as the best goalkeeper, while Dony Tri Pamungkas, also from Indonesia, was chosen as the best player.
Jake Najdovski from Australia was the top-scorer of the tournament.
Thailand still share the record for most Asean U19 titles with Australia. Both countries have won the tournament five times each.