I agree with the person above. VietnamGreen is incorrect. You do NOT have to get a Cambodian visa beforehand. You can get one on arrival, either at the airport or at a border crossing from Thailand.
For Vietnam, you can get on on arrival at the airport, or you need to apply for one if you are going overland. Here is some stuff from a previous entry I made just recently regarding this:
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VIETNAM VISA INFO
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Vietnam requires you to get a visa ahead of time and you must fill out their visa application available either online (just to download but not to submit application) or at your nearest Vietnamese consulate (embassy). If you cannot get to a consular, then you must send in the application to the embassy about 6 months prior to your visit.
Only citizens of certain countries can visit Vietnam without an entry visa (valid for visit within 30 days). Those countries include: most Asean countries, Korea, Japan & Scandinavians (2005). All other citizens are required to get an entry visa before departure or a pre-approved entry visa (visa is issued on arrival at Vietnam’s International Airports) supplied before arrival in Vietnam.
VISA ON ARRIVAL INFO:
In the event that there is no Vietnam embassy or Consulate in your country, or you just want to make Vietnam part of a multi-destination trip, then we recommend Visa on Arrival as your best option.
What is a 'Visa on Arrival ?': this is most likely the easiest way to obtain your visa without having to chase down embassies, consulates and the like prior to your trip, and is a valid alternative when applying for a tourist visa. The entry visa will be stamped on your passport as you pass through our immigration checkpoint. Though valid for thirty days, it can be extended once you enter Viet Nam. With this type of visa, you only can enter the country by air.
Should you wish to extend your visa, go to the Immigration Office at 40A Hang Bai St. in Hanoi, Tel: 826 6200. Many tour operators can also extend your visa for a fee.
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CAMBODIA VISA INFO:
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Cambodia Embassy in Thailand
No. 185 Rajdarmri Road, Lumpini Patumwan, Bangkok 10330, THAILAND
Entry visas are obtainable at Cambodian diplomatic missions and required for all visitors with valid passports irrespective of nationality. Cambodia, however, is very liberal with their visa regulations. You must bring with you: A Passport Photocopy ; 1 passport size color photo (3cm x 4 cm) and $20USD (cash only) for one-month tourist visa fee (Paid directly to the immigration). The visa validity is 30 days from the date of issue, NOT from the date of entry!
Recently, visa on arrival are widely applied in the airports and land-ports of Cambodia. Visitors no longer need to get the visa stamp at the Cambodian Embassy before your visit. Application form is distributed by the Government Immigration upon arrival. Its a no-hassle deal getting into Cambodia...but if you screw up in Cambodia, it could be difficult to get out. I suggest if you are an American, register with the US Dept of State. You can register your travels online so if you are missing, they might at least know where to find where you were last.
Cambodian Visa Extension
Travelers who would like to prolong their stay in Cambodia may extend their visa at the Department of Immigration situated just opposite the Pochentong Airport. The visa may be extended for 30 days at the cost of $25USD. Some travelers have reported that the visa extension for another one month was no longer possible, since the middle of June 2000. If you expect to stay more than a month, better get a Business visa at one shot for $25USD with three months validity.
I advise you to take this information for what its worth, but always be sure to do your own checking as things change in the part of the world on a daily basis. Good luck!
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