JAKARTA - Indonesia and defending champions Singapore booked their places in the semi-finals of the Southeast Asian championships with a game to spare after victories on Sunday. Indonesia thrashed Cambodia 4-0 and three-times champions Singapore beat Myanmar 3-1, sending both through on six points. Indonesia play Singapore on Tuesday to decide the group winners. Last year's player of the tournament and golden boot winner Noh Alam Shah put the Lions ahead after a minute and Agu Casmir scored a brace to take his tally to four goals in two matches. Myo Min Tun scored for Myanmar on 28 minutes. "We started well, but I think the second goal came a little too early and it caused the players to be too comfortable," Singapore coach Raddy Avramovic told reporters. Budi Sudarsono scored a hat trick for Indonesia, netting his fourth goal in two matches. He opened his account on 16 minutes but the co-hosts struggled to find their feet until 10 minutes into the second half when Sudarsono bagged his second. He got his hat-trick on 70 minutes and Bambang Pamungkas completed the rout soon after. Indonesia coach Benny Dollo admitted his side were out of sorts in the first hour of the match. "We really thought (Cambodia) would play defensively, so when they did otherwise, the boys were surprised and lost concentration," Dollo told reporters.