I am not sure that using AS miles as a primary program for travel on CX based out of SIN is wise, even if the miles are cheap at the present time.

AS's CX award chart for Europe, Africa/Middle East/India and Australia requires origination in HKG. This would mean you would need to use a second AS award, or alternate flights to get to HKG from SIN and v.v..

The award where it would be possible to originate in SIN is AS's North America-Asia award on CX, but that's a limited number of CX's destinations. There is also the problem of having very limited options intra-Asia for redemption of AS miles (basically, CX and KE, with KE having lots of blackout dates, plus perhaps DL going SIN-NRT-USA, but good luck with that- DL is notoriously stingy), as well as being limited to partner inventory only. I think having heavy investment in a program with limited redemption options at your location has some risks.

FWIW, US often sells miles at a price lower than or comparable to what AS is selling right now (in fact, they have a sale on right now), and *A partner premium class options for travel out of SIN are much better than CX/KE/DL (TG is nearly always available, for instance).

If you were to do go ahead and accumulate in AS, it might behoove you to also accumulate BA Avios, as their distance-based chart would help reduce costs for flying to HKG or BKK in premium cabins on award.