An increasing number of border crossings are open to foreigners travelling overland from Vietnam.
Currently there are fives: MocBai/Bavec, 200km southeast of Phnom Penh; Chau Doc/K’am Samnar on the bassac river; Tinh Bien/Phnom Penh near Ta Keo; Ha Tien/Kampot and the recently opened Trapeang Phlong east of kampong cham. Cambodian visas are issued on arrival at all points
. From Bavet, It’s easy to get shared taxis to Phnom Penh (about 3 hours). Phnom Penh Sorya Transport Company runs a twice-daily international bus service between Ho Chi Minh and Phnom Penh. From Chau Doc, there is an express boat (1 daily/ 5 hours) up the Mekong River direct to Phnom Penh in the morning.
Entering Cambodia at the other border crossings your transport options are at present more limited; Taxis run from Phnom Den to Takeo and Phnom Penh; While at Ha Tien You’ll most likely have to take a moto to Kep or Kampot.