By FOX Sports staff
Entering Wednesday's second leg at the Udon Thani Stadium leading 1-0 on aggregate, the Thunder Castle took just seven minutes to open the scoring when Adisak Kraisorn struck, before Spaniard Jesus Berrocal all but made sure of their progress with a second in the 72nd minute.
The hosts managed to pull one back five minutes from time through an Auttapol Wongsunthorn effort, but it proved to be a mere consolation as Buriram moved one step closer to retaining their title.
Fellow Thai Premier League outfit Ratchaburi are also through to the semis after a 2-2 draw against Chonburi was enough to see them progress 3-2 on aggregate.
With a one-goal lead from the first leg, many expected Ratchaburi to sit back and adopt a cautious approach but instead, they showed plenty of initiative from the opening whistle and took the lead in the 14th minute when Prayad Boonya ventured forward to score.
Three minutes before the break, the contest was all but over when Banluesak Yodyingyong netted to make it 3-0 on aggregate in favour of the Dragons, but Chonburi did keep alive their hopes of pulling off a miraculous comeback when Kraikitti In-Utane pulled one back in the 57th minute.
Jetsadakorn Hemdaeng then netted in the 71st minute to make it 2-2 on the night before Ratchaburi really looked in trouble six minutes from time when they had Jang Gil-hyeok sent off, although they ultimately held on to book their place in the last four.
There was no such luck for Army United however as a 2-0 defeat to Nakhon Ratchasima saw them eliminated 2-1 on aggregate.
Yusuke Kato struck after seven minutes to open the scoring for Nakhon Ratchasima and level the aggregate scores, before Douglas Carneiro popped up in the 56th minute to score what ultimately proved to be the winner.
To add insult to injury, Army were reduced to ten men 17 minutes from time when Chaiwat Nak-iem was handed his marching orders.
Finally, Rayong FC beat Looktabfab 2-1 to claim a 3-2 aggregate victory in the final last-eight tie.
Having played out a 1-1 draw in the first leg, it was Looktabfah who drew first blood on Wednesday as Wacharin Sombatwatanagun opened the scoring a minute before the break, only for Anukorn Sangram to equalise in the 51st minute.
Looktabfah were then reduced to ten men four minutes after the hour mark after Komsak Blieanminwai picked up a second booking and their opponents duly made their numerical advantage count, netting the winner 11 minutes from time through a strike from Piroj Anantanarong.
Wednesday's Thai League Cup Quarter-final Results
Looktabfah 1-2 Rayong FC (2-3 on agg.)
Nakhon Ratchasima 2-0 Army United (2-1 on agg.)
Chonburi 2-2 Ratchaburi (2-3 on agg.)
Udon Thani 1-2 Buriram United (1-2 on agg.)
Image courtesy of Buriram United FC