It has always been my approach in maximizing the cost of plane tickets to do border crossing to nearby countries of the country I am visiting. I did it in Hongkong to Macau, then Singapore to Malaysia and this time Vietnam to Cambodia.
Vietnam has over a dozen international overland border crossings. These allow overland travel to Cambodia via five crossings, the most popular of which is the Bavet / Moac Bai. This was the first crossing between Vietnam and Cambodia to open to foreign travelers and it remains easily the most popular. Daily buses regularly ply the Saigon - Phnom Penh route and the service is both fast and affordable.
We booked our Saigon - Phnom Penh -Saigon trip on March 20-22, 2010 via The Sinh Tourist Bus Company (at 246-248 De Tham Street, District 1 HCMC). Each way per person is $10 (inclusive of bottled water and wet tissue) on an A/C bus, with or without CR depending on which bus is assigned for the trip you booked. Departure time is at 6:30 am, arriving in Phnom Penh at 12:30 since the whole travel time on the bus plus the time at the exit point (Bavet) and entry point (Moac Bai)is six (6)hours.
We had a cheap, hassle -free travel since Filipinos do not need visa to enter Cambodia and re-enter in Vietnam unlike other foreign tourists like Americans and British. That saves us $20 for visa to Cambodia and another $20 for visa to Vietnam.
At the Bavet exit point, you will need to get all your luggage out of the bus and have them scanned at the immigration while getting your departure stamp. Taking pictures at this point is not allowed (but you can after you pass by the immigration officer). While on the bus, the conductor will hand out Departure Card forms which you will have to fill up and give back to the bus conductor along with your passport. The bus conductor hands All the departure cards to the immigration officer so you only have to wait until the conductor (who stands near the Immigration Officers) calls your name. This is the same situation in entering Vietnam.
Entering and leaving Phnom Penh through Moac Bai is a lot easier and faster because you do not need to bring your luggage to the immigration counter.
I really like my experience at the Bavet /Moac Bai border, both going to Phnom Penh and coming back to Saigon. For once, I feel lucky that I am a Filipino!