He must have been aware of the conditions attached to the issue of his air side pass, i.e. purposes connected with his employment only. The airport police even send out reminders from time to time of what this means
The airport pass is a security document issued to a person in his or her official capacity to access the security restricted areas in Changi Airport to perform his or her work. Any airport pass holder caught misusing an airport pass shall be arrested and prosecuted. Such offenders shall be liable on conviction to a fine of $1,000 or to imprisonment for a term of 2 years or to both. His or her eligibility for an airport pass in future will also be adversely affected.
As a local he would be aware of the strict application of the law in Singapore and deserves no sympathy.