Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Puerto Princesa to Siem Reap as you normally would.
Related info for your journey
Useful info, stats and facts about Puerto Princesa to Siem Reap flights.
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 Siem Reap Airport flight would often be abbreviated as a PPS to REP flight.