After drawing a blank over 90 minutes of play, the two nations duelled from the penalty spot to decide the winner. The shootout tilted in Thailand's favour when keeper Kawin Thamsatchanan saved an attempt by Artsiom Skitau before Srirod Chatthong netted his shot to propel Thailand to victory.
The win also marked the first trophy for Milovan Rajevac, who took over as Thai team manager less than two months ago.
The third-place playoff earlier on Sunday saw Burkina Faso beat North Korea 4-3 in a penalty shoot-out after the teams ended 90 minutes with the score at 3-3.
Goalkeeper Aboubacar Sawadogo saved two attempts by North Korean players and then sealed the victory by sending home the last penalty.