Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Bangkok to Burundi as you normally would.
Related info for your journey
Useful info, stats and facts about Bangkok to Burundi flights.
Great question - BKK to BJM just means Bangkok Suvarnabhumi Airport to Bujumbura Airport. Now you’ll know what these unique codes when you look for flights! Bangkok Don Mueang Intl Airport (DMK), Rayong Utapao Rayong Pattaya Airport (UTP), Hua Hin Airport (HHQ) are other airports near this flight route and their unique identifiers/IATA codes.