The victory was the first for Thailand since Milovan Rajevac took up his post as national coach in May.
Playing in front of 10,000 fans, the host team took the lead when the brilliant Mongkol Tossakrai blasted home from distance in the 41st minute.
Mongkol Tossakrai
The Pattaya United winger also scored here for Thailand last month during the World Cup Asian qualifier against the United Arab Emirates.
Chiangrai United’s Thitiphan Puangjan scored the second goal for the Kingdom in the 78th minute before substitute Teeratep Winothai extended the Thai lead to 3-0 with a penalty during injury time.
Thailand will play Belarus, who earlier today beat Burkina Faso in a shoot-out 3-0, in Sunday’s final at 7.30pm. North Korea will face the African nation in the third-place play-off at 4.30pm.
Thitiphan Puangjan
Teeratep Winothai