Most visitors to Cambodia require a one-month tourist visa (US$20), although some visitors enter on a one-month business visa (US$25). Most nationalities receive a one-month visa on arrival at the International airport in the capital city Phnompenh and Siem Reap – a home province of Angkor Complex and at land borders. One passport-sized photo is required and you will have to pay 1 US$ if you do not have one. It is also possible to arrange a visa through Cambodian embassies overseas or an online e-visa (US$25) through the Ministry of Foreign Affairs. Arranging a visa ahead of time can help prevent potential overcharging at some land crossings.
Those seeking work in Cambodia should opt for the business visa as, officially, it is easily extended for long periods and, unofficially, can be extended indefinitely, including multiple entries and exits. A tourist visa can be extended only once and only for one month and does not allow for re-entry.
Cambodia visa could also get at Poit Pet border gate with Thailand when you drive in from Thailand or at Chau Doc when you border gate with Vietnam by the boat trip from Vietnam) or from another border with called Moc Bai or Bavet in Cambodia. The Visa fee from these place is 23 US$ per persons for Single entry.
Visa extensions are issued by the large immigration office located directly across the road from Phnompenh International Airport.
There are two ways of getting an extension (one official and one unofficial) and, unsurprisingly, the time and money involved differ greatly. Officially, a one-month extension costs 35 US$, three months 65 US$, six months 125 US$, and one year 200 US$, your passport will be held for 25 days and there will be more paperwork than a communist bureaucrat could dream up. This is fine for expats with an employer to make the arrangements, but those on their own really need to go unofficial. They do not call it corruption in Cambodia but “under the table” and you can have your passport back the next day for the inflated prices of 45 US$ for one month, 80 US$ for three months, 165 US$ for six months and 265 US$ for one year. Once you are one of the unofficials, it is pretty straightforward to extend the visa ad infinitum. Travel agencies and some motorbike rental shops in Phnom Penh can help with arrangements, sometimes at a discounted price.