
Thailand chalked up an aggregate score of 3-1 after winning 1-0 in the first leg match held in Jakarta.
Thailand will meet either Singapore or Vietnam in the final when both teams will play in the other second leg semi-final match at Singapore's National Stadium on Sunday.
Singapore held Vietnam to a goalless draw in Hanoi on Wednesday.
The Lions are hoping to win the 4th Asean Cup title and make it three successive wins in the competition.