Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Kota Bharu to Adelaide as you normally would.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Kota Bharu Pengkalan Chepa Airport to Adelaide Airport flight would often be abbreviated as a KBR to ADL flight.