from web site
Singapore Airlines Refund Policy for Non-Refundable Tickets
The non-refundable tickets refund policy of Singapore Airlines is a plan to give some flexibility between the traveler and the airline in very limited specific cases while keeping to the fare rules of cheap tickets. As a rule, non-refundable fares are not entitled to a full cash refund if you decide to cancel your trip voluntarily. Nevertheless, the travelers might still be able to get part of their money back or have some fees waived depending on the case. In general, the passengers are allowed to claim back the government taxes and airport fees that were not used even if the base fare was non-refundable. The airline normally pays these amounts after taking off the relevant service charges.
link:-https://lowestairlinesdeal.com/singapore-airlines-refund-policy/