Visas on arrival

Phnom Penh
It's all quick. You provide a passport size photo, they take one with a digial webcam and the scan your thumbs and four fingers, hand in the visa application form given on the plane, and queue to pay the fee and collect the passport which goes from one person to another , for up to 4 or 5 of them, to be called.
Watch the change if you pay with a 50$ note as it's a common scam to be given 5$ less. First hand info! I counted the change right there in front of them and i was 5$ short and told them so. No questions asked, they give you the correct amount. Cheeky monkeys.
It costs 20$.

Laos
Simple but more rudimentary. Basically no scanning nor digital photo. You provide a photo, fill in a form there on the spot with little space to do it.
different fees for different nationalities. Spanish 35$ + 1$ for service (can you believe it?)
After, immigration and your entry form.

vietnam
NO visa on arrival unless you've applied for an e-visa.
We had our visa done in Madrid. 65$ for one entry. 80$ for double entry.
It takes a week or so.