This is a PSA for those who might not know, but I made the mistake of booking a one-way airfare from BKK-Airport to Clark and was told at the check-in counter that I must purchase a return flight in order to not have a problem with Immigration at a Philippines airport.
I thought I'd leave it open in case I wanted to explore Boracay, Cebu, etc. so didn't purchase the return flight. At the counter, I purchased a return from Manila three days later. I've decided to extend my stay here in AC through Saturday. I had to pay a penalty fee of 3414 Pesos fee to change my flight and airport, even for a less expensive ticket. All around, this error cost me about $175 USD vs. a simple RT booking from BKK-Clark.
Anyway, even if this reaches the less than 1% who are unaware, if a foreigner travels into the Philippines, s/he must have a return ticket and this must be presented to Immigration at the PI airport.
Perhaps some of the more senior members can elaborate on this PI immigration policy.
I'm having a blast in AC and will file a detailed report in the near future.