I cancelled my ticketed 6th June flight on 14th May. Got the refund notice and miles in on 12 June at 11.15pm. Took around 4 weeks.

On 6th June, I called up KrisFlyer to make a redemption booking on SQ flights, departing 01 July to ZRH. I need the miles from the cancelled flights because I am short of some miles to issue the ticket. So I requested to the CSO to make a urgent request to expedite. The ticketing deadline was 17 June. Maybe that's why my refund was faster than usual. You can try my method. I cancelled the ZRH flights after I got my miles back.