You will need to click on the "here" link under Travel Waiver Policies to access the .pdf for the full information, but below is the guts of it:
Singapore Airlines is waiving all rebooking fees for tickets issued on or before 15 March
2020, for travel up to 31 May 2020, with immediate effect. Customers can cancel their
existing flight itineraries, retain the value of their tickets and rebook their travel at a later
date, when they are able to firm up their new travel plans. The new flight itinerary should
be completed by 31 March 2021.
This new policy will allow customers the flexibility to defer their travel plans and applies to
all bookings for travel up to 31 May 2020. All rebooking fees will be waived, although a
fare difference may apply for the new itinerary.
SIA will continue to review its waiver policy and retains the flexibility to extend the cut-off
date of 31 May 2020 as it assesses the impact of the Covid-19 outbreak on global air travel
in the coming weeks. For all new SIA and SilkAir tickets issued from now to 31 March 2020,
SIA will also waive change fees.