Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Doha to Pisa as you normally would.
Related info for your journey
Useful info, stats and facts about Doha to Pisa flights.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Doha Hamad Intl Airport to Pisa Gal Galilei Airport flight would often be abbreviated as a DOH to PSA flight.