When I got off the bus that takes you across the Thai-Lao Friendship Bridge, I was the only person who needed a visa-on-arrival so I thought it would be quick. But I arrived during the "dinner break" of the people doing that job and had to wait around for twenty minutes!
Only when the guy eventually appeared could I get the entry forms, which took some more time to fill out. But the guy was cheerful and his English was good. I told him I didn't have the photo mentioned on the form and he said:
I also left some fields blank on the form such as previous and next destination, which are fuzzy or unknown since I'm hitchhiking without a plan and because I didn't know where I'd been staying and there fields for address and phone number where you're staying, and also of a Lao contact.
This was also no problem.
I was concerned "no problem" might mean some unofficial charge was coming up. They did not have a camera and did not take my photo (unless they took it from a security camera), and there is no photo on the visa itself.
The charges were only:
- The $30 USD visa fee
(Australian citizen price, other nationalities may have other prices)
- Another $1 USD fee
Some websites, as referenced in HaLaBi's answer talk about a $1 fee when you don't have a passport photo. I believe they're confused as the receipt for this $1 fee clearly states "Friendship Bridge I (FOR FOREIGN PASSENGER)":
The fees should be paid in USD. If you pay in Thai Baht you will be required to pay 40 baht per dollar. For comparison, the actual exchange rate today is 32.25 Baht per dollar. I didn't bring any $1 bills so paid only the bridge fee in baht.
Some other people may have paid a photo fee but I doubt it. Some nationalities might need the photo, but as an Australian it was no problem and there were no fees or bribes.