Koh Kong, Cambodia

Coming across from the Thai Border
Cambodia offers most countries citizens a visa on arrival to the country. Most common are tourist and business visas. These cost between $20 and $35 dollars and are generally valid for 30 days. You're also required to have 1 passport sized photo.   Usually they demand 1,000 Baht ($30 U.S.) or more Thai money for a tourist visa and more for a business visa.

Quite often, the border guards or a "Doctor" require some certification of not having some disease, like pig flu or yellow fever.  Since nobody has one, they'll accept a small contribution of 20 Baht to 3 dollars (or more?) to provide you with one.   The latest, is a 1 second medical check with a laser thermometer. 
                    Welcome to Cambodia!

If there are not many people coming across when you are crossing the border, both the Thai and Cambodian sides of the border only take a few minutes each.  If there's many people, like when a bus comes to the border, it can take an hour or more on each side.  No bribes are necessaries or requested on the Thai side of the border, but you do need all your paperwork in order..

A vehicle registered in Thailand can be brought across the border only if you have the vehicle registered in your name. And there are many other qualifications as well.  It's very problematic now, and if you have Thai license plates, you might want to think twice about bringing a vehicle over the border.  Charges, which should be free, are generally 100 Thai Baht per day. You can also leave a vehicle parked on the Thai side of the border for 200 Baht per day.

Current exchange rates: $1 U.S. = 30 Thai Baht ......... $1 U.S. = 4,000 Cambodian Riel

Hours of operation.
The immigration office is generally open from 7am to 8pm, everyday.  However, on the Thai side of the border, transportation to and from Trat, the first big town in Thailand, stops at 5pm.