I have always been asked to show onward ticket when travelling to the Philippines and Indonesia out of HKG by ALL LCC check-in clerk.

As these are my NGO business we might buy inbound with one carrier and outbound with a different one due to cost. Have a printout of your onward ticket as email confirmation or phone apps on devices are not sufficient for many.

The only airline that did not ask for onward for these countries when checking in a oneway was CX/KA out of HKG. Probably due to my status with them? We usually buy inbound with CX/KA for luggage allowance and fly back empty-handed.