Thailand coach Worrawoot Srimakha has warned his players they must work hard to earn places in the SEA Games squad.
A total of 26 players are in the training camp. The number will be trimmed to 20 ahead of this month's SEA Games in Malaysia.
"Nobody is assured of a place in the team,'' Worrawut warned yesterday.
"Everybody has to work hard during training to be included. It depends on their training and fitness levels."
However, the coach said those who can play in several positions are likely to be picked.
The Thais will play a warm-up game with Hong Kong's Eastern Sport Club tomorrow and leave for Kuala Lumpur on Saturday.
Two-time defending champions Thailand are in Group B with Cambodia, Indonesia, the Philippines, East Timor and Vietnam.
Group A consists of Malaysia, Myanmar, Singapore, Laos and Brunei.
The top two teams of each group advance to the semi-finals.
The Thais will begin the defence of their title against Indonesia on Aug 15 in the U22 football tournament at the biennial event.
Goalkeeper Nont Muangngam, who formerly played for France's U16 side, believes the gold medal is attainable.
"This would be my first SEA Games. If I am selected I only have one goal: gold. I'm ready," said the 20-year-old Chiang Rai United player.
Nont is likely to make the 20-man squad after Port goalie Rattanai Songsangchan pulled out earlier.
BeIN Sports app
BeIN Sports has launched BeIN Sports Connect, a new application to watch live football matches.
The app gives Thai fans access to several major tournaments including the English Premier League, Uefa Champions League, Europa League, Spain's La Liga, Italy's Serie A and Ligue 1 in France.
Thailand is the first Asian market to enjoy the service, the company said.
It can be download at the App Store and on Google Play as well as through www.connect-th.beinsports.com.