Thailand went ahead two minutes into the game when midfielder Iklas Sanron picked up the ball on the left and then wove his way into the box before firing into the far corner, reports the Bangkok Post.
Thailand continued to dominate as Siraphop Wandee went close with a curling shot that forced Mongolia goalkeeper Chinmargad Bat-Erdene to tip the ball to safety.
The home team doubled the lead in the 18th minute when Iklas spotted Bat-Erdene racing out of his box and prodded the ball towards an empty goalmouth with captain Seksan Ratree arriving to slot home for a 2-0 lead.
Seksan made it 3-0 in the 39th minute, capitalising on a poor Mongolia clearance to curl a spectacular shot that gave Bat-Erdene no chance.
The skipper completed his hat-trick in the 57th minute, slotting home from close range after his initial header was saved by Bat-Erdene.
Chawanwith Saelao and Yotsakorn Burapha were on target in the 68th and 82nd minutes as Thailand wrapped up a convincing victory in their opening match.
“We achieved our goal, which was to get three points in our first game,” said Thailand U23 head coach Thawatchai Dumrong-ongtrakul.
“I must commend them for their consistent pressure. Getting the early goal made it easier for us to play and create more attacking space. It’s important that we don’t underestimate our opponents and maintain focus at all times, and they did well.”
Thawatchai praised hat-trick hero Seksan and first-timer Iklas for their contribution.
“He [Iklas] has talent, speed and strength. Today he passed the test, but he still needs a lot of work. Scoring in the first match gives him confidence, but the next game against Lebanon will be even tougher.”
Thailand will play their second group game against Lebanon tomorrow, with the West Asian side also on three points having won 1-0 against Malaysia.