I've found Google Flights is the most 'honest' of all the ticket broker sites, because Kayak, SkyScanner and the rest of them, if they see referral or cookies in your browser from other cheap flights sites they will hide the best deals. Make sure to always clear out your browser history completely if you're checking multiple sites.
Another well known trick is use local IP. If you can get a Philippines VPN, or Thai VPN, then look at airline sites directly (like say, get Thai VPN then go to Thai airlines page) you will notice prices are lower as they are priced for locals, and inflated when you land on there with your European or US IP. Often with this method you get at least $200 off, and things like 'preferred seating' will be much cheaper, my reg IP they quoted $160 extra to get a legroom seat, local IP it was only $20.
There is also the booking two one-way flights scheme if the country allows this, some countries don't let you enter one-way. Often an airline will quote you a really cheap one way flight to the Philippines then ridiculous amount on return, because that's where they make up the rest of their money. Use your regular internet to book Your Country->Manila, then load up Philippines VPN, and book one-way back MNL->Your Country. Often can save hundreds this way (clear all cookies too).
Note, some airlines got hip to this scheme and now ask you to enter local identification info, like CPF number if flying Brazil airlines when booking to lock out the foreigners who don't want to get scammed by their inflated pricing. In that case you'd need a local you trust to book it for you.
Also, sometimes just changing your location on the airline website and not even bothering to use a VPN will work as it did here: http://www.businessinsider.com/use-a-fake-location-for-cheap-airfare-2014-6