Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Puerto Princesa to Palau as you normally would.
Puerto Princesa (PPS), located 25.0 km from the city center, is the airport you fly out of when you book flights from Puerto Princesa to Palau.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Puerto Princesa Airport to Koror Airai Airport flight would often be abbreviated as a PPS to ROR flight.