AFF Suzuki Cup: Thailand 2 Malaysia 0 (3-1 agg)
The two sides drew 1-1 in the first leg, but Teerasil Dangda and Theerathon Bunmathan scored two second half goals in four minutes the seal the 3-1 aggregate win.
The three-times winners have been present in five of the eight finals since the tournament's inception in 1996 and will now contest their ninth over two legs against Singapore.
With their last four clash closely poised at 1-1 after Sunday's opening leg, Malaysia and Thailand had everything to play for in Bangkok.
But Malaysia's chances of progression suffered a setback on 44 minutes when Mohd Fadhli Mohd Shas was sent off for a second bookable offence.
Replays showed he shoved Datsakorn Thonglao, who also received a booking, but it was advantage Thailand going into the second half.
After the break, the hosts took just 20 minutes to break the deadlock, with Dangda capitalising on some poor defending to slot past the goalkeeper.
Bunmathan then made it 2-0 four minutes later, tapping home the spilled ball from Jakkraphan Pornsai's free-kick.
The first leg of the final takes place in Singapore on December 29, with the return leg back in Bangkok three days later.