[2] In 2012, while playing for the LionsXII, Shahdan Sulaiman's impressive form had attracted the attention of the Thai scouts from Pattaya United F.C.

[7] Shahdan played a key role in the team, starting 10 out of 10 league games for the stags before he then missed a huge chunk of the season due to an injury that he picked up in the 90th minute of an AFC Cup tie with Selangor at the Singapore Sports Hub.

[10] He had a good season, scoring 6 goals in all competitions, with his performances attracting interest from MSL side Melaka United.

[15] On 18 April 2022, He assisted Pedro Henrique goal from a corner with a famous victory over Korean club, Daegu FC in the AFC Champions League.

Shahdan signed for the Cheetahs ahead of the 2023 SPL season but suffered a fractured fibula and dislocation of his left ankle during pre-season which meant that he missed most of the campaign.

[16] However, he overcame these issues and established himself as a key player for Hougang United in the 2024 Singapore Premier League season with one goal and three assists from 14 appearances.

[16] Shahdan got his first goal for the national team in a 2–2 draw with Azerbaijan, scoring a last gasp equaliser to help the Lions come back from behind.