The best way is to have all your documentation ready when you go to the SQ ticketing office. SQ is infamous for giving people the runaround... or that you'd have to call so and so to get the refund etc.

For the KUL-SIN-KUL ticket though, did you cancel your reservation or deferred to another date or kept 'open'. E-tickets cannot be issued as 'open'. If you no-showed the flight or cancelled within 24 hours of the original flight, please note that you might be liable to another S$150 penalty!