A controversial penalty 13 minutes from time saw Abdullah Al Hamdan guide Saudi Arabia to the last four and break the hearts of a capacity crowd at Thammasat Stadium.
It was hosts Thailand’s first-ever appearance in the knockout phase of the competition and they were hoping to claim one of the 2020 Olympic spots the tournament offers to the top three sides.
The FAT would not label the letter a “protest” yesterday (Jan 19).
“We are seeking explanations for certain rulings that went against Thailand during their AFC U23 Championship quarter-final match with Saudi Arabia on Saturday,” FAT said in a statement.
“There were incidents wherein the Thai players were handed yellow cards by the match referee, while the Saudi players were not penalised for similar offences.
“We also want to know the rationale behind selecting a team of match officials from the region of a country which is involved in a match.
“The FAT has also sought an explanation from the VAR referee as to under which clause of the rule book he awarded the penalty to Saudi Arabia.”
Al Hamdan scored from the spot after he had been pulled back on his way into the area, with referee Ahmed Al Kaf awarding the penalty after confirmation of the offence by VAR officials.
Replays showed the incident took place outside the penalty area.
The goal was a cruel blow for Akira Nishino's team, but the veteran Japanese coach said the Thai players would learn from their involvement in the knockout phase of the event.
“This was our fourth game and neither side was able to show the football they wanted, but our players worked hard and we were a bit more tired than our opponents,” Nishino said.
“For the first 15 to 20 minutes, we were able to press our opponent as we had planned and I don't want to say that one incident changed the game. These past four games have been good experience for the players.
“The 2026 World Cup is a target for Thai football and for this age group, this was good experience. If we can keep it up we will see how we do in the future.”
Saudi Arabia coach Saad Al Shehri said: “Thailand didn't have too many chances to score goals. If we didn't have the penalty, we have more good players outside who can come and maybe the game would have gone to extra time.
“But this is football. We had the penalty and we scored and then we had three more chances. We will take the win, this is very important.”
In the other quarter-final games, Australia edged Syria 1-0 on Saturday night and South Korea beat Jordan 2-1 yesterday.