[3] Hassan admitted in an interview with The Straits Times that he initially thought the ranking was a late April Fool's joke.

In 2004, Hassan joined the newly created team Young Lions alongside Baihakki Khaizan, Shahril Ishak and Khairul Amri where he is part of the 'NFA Gang of Four'.

[6] After completing his compulsory National Service in 2006, Hassan returned to Geylang United where he became the first-choice goalkeeper at the club.

On March 10, 2011, Hassan made his 100th appearance for the club in a league match against Tanjong Pagar United FC.

In December 2011, Hassan joined SAFFC (Singapore Armed Forces FC), after four years of service as Tampines Rovers' first-choice goalkeeper.

Hassan would go on to make his AFC Cup debut against Indonesian club Semen Padang in a 3–1 loss on March 5, 2013.

[9] He played for Gainare in two friendly matches during the brief stint, including about 70 minutes of a 3–3 draw with South Korean side Incheon United.

He made his AFC Champions League debut on April 15, 2022 against Urawa Red Diamonds and kept three clean sheets in six matches during the club's group stage campaign.

Hassan was a regular player for almost two decades in the national team and played in the 2010 FIFA World Cup qualifiers.

[23] His performance against Thailand garnered significant attention from Chinese fans, many of whom made donations to his nasi padang stall.

Following the 2026 FIFA World Cup qualifiers, Hassan went viral on Chinese social media and received numerous monetary donations at his nasi padang stall.

[30][31][32][33] After a scam attempt involving the QR code at his stall, Hassan asked fans to stop sending money and announced his intention to donate the received funds to charity.