Thailand U23 football team coach Issara Sritaro apologised to fans after his men were thrashed 4-0 by South Korea at the Asian Games on Thursday.
South Korea, who hammered Kuwait 9-0 in their opening Group E game, scored four goals in the first half at the Jinhua Sports Centre Stadium through Hong Hyun-Seok, An Jae-Jun, Um Wong-San and Lee Jae-Ik.
In the other Group E match, Bahrain drew 1-1 with Kuwait.
Thailand have one point from two games after a 1-1 draw with Bahrain in their first match.
Tomorrow, Thailand face Kuwait and defending champions South Korea take on Bahrain.
The top two teams in each of six groups plus four best third-place sides reach the round of 16.
"I have to apologise to my country for conceding four goals," Issara said.
"Our players did their best and played well in the second half."
Issara made several changes to the starting line-up but was forced to bring on key players in the second half.
"For the game against Kuwait, it is important for our players to regain fitness," he said.
Thailand are still looking for their first ever medal in men's football, having finished fourth four times in 1990, 1998, 2002 and 2014.
The 19th Asian Games officially open today but some events have begun their preliminary phase, including football.