Brisbane Roar FC
Siwarak played in the 2013 AFC Champions League playoffs against Brisbane Roar FC, from his team's Thai FA Cup win. Siwarak's form in the 2013 AFC Champions League playoffs was extraordinary, after getting a clean sheet and saving three penalties in a row from players from Brisbane Roar FC. Buriram United qualified to 2013 AFC Champions League after winning Brisbane Roar FC in the penalty shootouts. After that Siwarak became number five of Asia in saving the most penalties. He played every game for Buriram United in the 2013 AFC Champions League. Siwarak also played every game for Buriram United in the 2013 Thai Premier League, he conceded 23 goals and got 13 clean sheets.