Playmaker Chanathip Songkrasin pulled out of the Thai squad for the King's Cup on Friday due to an injury.
The midfielder tore a muscle during training at his Japanese club Consadole Sapporo this week.
Thailand coach Sirisak Yodyardthai has called up Buriram United's Supachok Sarachart to replace him.
The 47th King's Cup will be held at Buriram United's Chang Arena from June 5-8.
Thailand will open their campaign against Southeast Asian rivals Vietnam and India take on Curacao on the opening day of the prestigious event.
The winners will meet in the final and the losers play in the third-place play-off on June 8.
"A check-up found that I have a torn muscle," Chanathip said.
"I have to take one week of rest so I had to withdraw from the national team.
"Initially, I wanted to play for my club on June 1 to prove that I was fit enough to play for the national team.
"However, the club said it was impossible and they did not want me to take any risk."
The 25-year-old added: "It is a pity that I cannot play for the national team. All I can do is give the players moral support. Although winning the title is difficult, I am sure that everyone will give their best."
Coach Sirisak said: "It is a pity because Chanathip is one of our main players. This will surely affect our team.
"But we play as a team, and I am sure that his replacement will be able to deliver.
"It is also a good opportunity for other players to prove themselves.
"Supachok's style is similar to Chanathip's. I think he will do well at the King's Cup."
The 21-year-old Buriram star has played one match for the national team.
He has been a key member of Thailand's U23 side.
