Please advise where I can buy a cheap ticket to travel to Manila and back.

I would advise you to check on-line as this is where the best offers are found.  Check out sites such as Yalago and Expedia.  It is sometimes cheaper going via another destination rather than direct.  It may also be worth checking out some of the travel agents in the Satwa area as they deal with a lot of clients returning to the Philippines so maybe able to avail of some good deals.