The cheapest flights between Bangkok and Manila are starting to come down before finding a flight under $300 was quite a chore. then last year durringthe Fuel price spike the flights got expensive now there are deals on cheap flights from Singapore and Bangkok to Angeles City. The last time that I went to the Philippines I ended up flying from Bangkok to Singapore and then to Clark air force base in Angeles city which is where allot of the regional carriers service.
You can also go from Bangkok to Kuala Lumpur and then on to Angeles City another option now is to route out of Saigon Vietnam using Cebu Pacific I pretty much wasted a day but the $100 dollars was worth it a added benefit is getting to stay in a night in one of my favorite cities Singapore.

The flights that I took was Air Asia from Bangkok to Singapore and then I took Tiger Air to Angeles City. I then took a bus that I caught just outside of the Angeles City airport which you have to take a taxi too and I might add that it is a rip off but there is nothing you can do about it as it is way to far to walk. Having a hotel pick you up is a good idea Margarita Station website where you can make reservations for Angeles City Hotels and arrange pick up from the Clark Airbase.