Your mileage may vary on this depending on what citizenship you have so check that further on the site I link below.
My recommendation if you are coming here is to apply for an e-visa and staying up to 30 days and applying at least two days before entering Cambodia what you need is found on this official site https://www.evisa.gov.kh current cost when writing this is 36 USD the fee for visa is 30 + 6 processing fee = 36 you pay this online while applying – be sure when doing this that you get all the questions correct because it’s NOT refundable unless they do something wrong and you didn’t.
So you got the approval email – print before traveling it in TWO copies of the certificate black and white is accepted and bring those – that’s it for the Visa part go ahead and book your trip if you haven’t already. You do NOT need extra passport photos with e-visa.
You will get a arrival card on the flight as well as a declaration form you need your basic passport number – where you stay in Cambodia- hotel name is sufficient – your e-visa number that you find on your …e-visa rest is just name and other info see picture
Declaration form is for currency and other things you may want to declare – remember answer truthfully.
So you have flown to Cambodia and maybe arrived in Phnom Penh international airport – you are heading into the arrival hall and will probably see a long queue of people standing in line for visa on arrival – that is NOT for you – you can head directly to immigration and present your
2. your arrival card fully filled in
3. One of the printed e-visas – the second you show when leaving Cambodia.
Absolutely no money will be paid at immigration if you do the above – you are all set to go when you get your stamps in your passport- be sure to have the arrival card and the e-visa copy with you you give that back when exiting.
Remember the declaration form? Get you bags if you checked anyone in on the assigned belt of your flight. After that you will hand the fully filled – backside is for if you need to declare something – over to an airport officer clearly marked at exit and you are on your way.
This guide applies to arrival by air – yes it matters. And this was experienced July 29 2019.