A one-way flight to Manila is the perfect start to an open-ended island trip. You can spend a week in Palawan, extend your stay in Siargao, and decide where to go next once you know which beach you like best. There is just one detail worth organizing before you reach the airport: your proof of departure from the Philippines.
For many short-stay visitors, the Philippine government's published visa-free entry requirements include a valid return ticket or an onward ticket to another destination. That is separate from the flight that gets you into the country. If your itinerary stops at Manila, Cebu, or another Philippine airport, the airline may ask to see what comes next.