Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Jakarta to Brittany as you normally would.
Jakarta Soekarno-Hatta Intl Airport is CGK and Rennes St Jacques Airport is RNS. These codes are created by the International Air Transport Association (IATA) and airlines use them to identify the departing and arrival airports in the flight routes they service. While you’re still figuring out your travel plans, it’s not a bad idea to learn the names and codes of other airports around these areas: Brest Guipavas Airport (BES), Lorient Lann Bihoue Airport (LRT), Quimper Pluguffan Airport (UIP), Dinard Pleurtuit Airport (DNR), Lannion Servel Airport (LAI).