That is correct. Asiamiles is free but Marco Polo Club costs USD50 to join (however you don't need to join MPC, but don't earn any status without being a member). There are many quirks to Asiamiles which makes it hard to compare to other programs, but in general it is worth about half as much as Aadvantage, so you might have orphaned Asiamiles if you don't fly more with CX on discounted fares (generally you would be better off crediting non-discounted fares to AA). HKG-DPS is only 2K+ miles, so you'll have to make 20 more trips like that before it becomes enough miles to do much with.