Bus: As the Kandal province is very closed to Phnom Penh there is several options to go there depending in which direction you would like to go. Irrespective where you would like to go you’ll find a vehicle at the central bus station southwest from the Central Market. Many buses go to the other provinces so they always have to pass Kandal province. If you would like to go to the provincial capital Ta Khmau there is Sorya buses going to the provincial capital of Takeo every day at 7am, 8am, 12am and 1pm. It shouldn’t cost you more than US$0.5-1.
Lots of share taxis leave unscheduled every day to Ta Khmau opposite from the central bus station. The prices are around US$1-2.
Almost every Highway around Phnom Penh is in best condition, so no worries. Riding your motorbike to Ta Khmau you have to take National Highway No 2 to the South. If you would like to hit the road to the North you have to take the National Highways No 4 or 5, depending on your destination.
For the time being, there is no flights schedule and airport to Banteay Meanchey, only main destinations in Cambodia offer you affordable flight and quick more easy.