For certificates from training providers: Contact the training provider directly. You will need a police report for the lost certificate, the training provider may mark the replacement as “reprint” and administrative fees may apply.
For old Occupational Safety & Health Training Centre (OSHTC) certificates: MOM cannot replace these as OSHTC ceased operation in Apr 2006. Workers can print their training records from the Check WSH training records eService. Note that most OSHTC certificates should have expired by now.