Using frequent flyer miles to get there can be a great deal, particularly as some programs don't classify CMB as being in South Asia and instead place it in the same zone as SE Asia for mileage redemption purposes.

A cheap paid ticket to say Japan or elsewhere in East Asia + an award ticket to CMB can help keep costs under control. (The downside is that it may require re-checking luggage and re-checking in at say NRT, BKK or SIN.)