By FOX Sports staff
Both sides are currently challenging for the league crown, with leaders Buriram holding a three-point advantage over their second-placed challengers.
Muangthong produced an epic comeback last month to book their place in the last four after overcoming a three-goal deficit at the break to beat PTT Rayong 4-3 after extra-time, while the Thunder Castle cruised to a 3-0 victory over Singhtarua.
And although many were hoping both sides would eventually meet in what would have been a dream final, that will not be the case after Thursday's draw pitted them against one another in the last four.
The game will take place on September 25 at the neutral venue of the Thammasat Stadium, although the game could be postponed if Buriram managed to overcome a 1-0 first-leg deficit in their AFC Champions League last-eight clash against Esteghlal and progress to the semis.
Both sides have met twice in the league already in 2013 with Buriram winning the first encounter 2-1 at the SCG Stadium back on April 17, before they played out a 1-1 draw in the return game on August 11.
The other semi-final will also witness an all-Premier League encounter between Police United and Bangkok Glass at the Rajamangala Stadium.
The Glass Rabbits are currently seventh in the league while Police are two places below them, and - having made it this far - both sides will be looking at the FA Cup as a legitimate avenue to end the campaign with silverware.
Bangkok Glass booked their place in the last four after claiming a hard-fought 1-0 victory at Bangkok FC, while their upcoming opponents needed a 3-1 penalty shootout win to see off Chiangrai United after both sides had played out a 0-0 draw last month.
Image courtesy of Buriram United FC