Thailand failed to earn a ticket to the 2023 Fifa U17 World Cup and the country could be punished after their fans lit flares at the stadium on Sunday night.
The Thais lost 4-1 to South Korea in the AFC U17 Asian Cup quarter-finals at Pathum Thani Stadium.
The defeat ended Thailand's hopes of reaching the finals for the third time after their appearances in 1997 and 1999.
The top four teams from U17 Asian Cup earn spots at the finals in Indonesia.
South Korea got four goals from Kang Min-Woo in the fourth minute, Kim Myung-Jun (36), Yun Do-Young (69) and Kim Hyun-Min (84).
Dutsadee Buranajutanon scored for Thailand in the 16th minute.
"We have to apologise to all Thai fans," said Thailand coach Pipob On-mo.
"Our boys did their best. They did everything they could. They scored in every game.
"I am so proud of the boys."
The 44-year-old former Thailand international urged his charges to keep improving and strive to fulfil their potential by making it to the senior national team.
During the match, sections of Thai fans at the stadium lit flares which is prohibited and the host country could face sanctions.
Football Association of Thailand (FAT) president Somyot Poompunmuang said he had asked all involved parties to gather evidence which could lead to the arrest of the culprits.
He also called on fans who had any clip of the incident to send it to the FAT.