China Eastern has long lead the way with their super cheap fares to Asia. Lately fares have been around $50 on the cheapest days. Today I see them the first time under $400 to South-East Asia.
While China Eastern is certainly not my favorite airlines you get a lot of time in the air for your money. Transfers are in Shanghai and since you are going to Bangkok/ Manila – the visa exemption is not an issue at all for a quick city sightseeing.