I just did the exact same thing, 60 day visa exempt but 84 day return flight. l had no issues with anyone and getting the 30 day extension (which l only did this week in Udon Thani) was a breeze.
l had heard that other offices weren't terribly user friendly, which was why l was happy to share my positive experience here about the Udon Thani office.
Thanks captain obvious. You really sound like a miserable know it all with a large chip on your shoulder. No one cheated anyone and they didn't just decide to steal money from me as you are suggesting. They charged 100 baht, which is absolutely bugger all, for a service that l was very happy to pay.
there is a bus that goes from Udon Thani bus terminal number 2 to Vientiane. I've not gone on it, but they say at the terminal where you buy the ticket that you must already have a Laos visa.