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.

In 2013 Siwarak played against Lebanon in the 2015 AFC Asian Cup qualification, after the first choice keeper Kawin Thamsatchanan got injured.

Siwarak was named for the final squad in 2019 AFC Asian Cup, but initially only acted as third-choice behind regular Chatchai Budprom under Milovan Rajevac.

Siwarak performance in later matches against Bahrain (1–0),[2] UAE (1–1)[3] and China (1–2)[4] earned him praises and reputations, in which he was accredited as an instrumental part for Thailand's return to the knockout stage since 1972.