He's not, he's Dutch. I would take what Luit van der Linde says with a grain of salt. He's a bit of a narcissist who makes up claims like there being some sort of agreement where you can hold only one driver's license worldwide or some nonsense like that. Such a rule simply doesn't exist but if you tell him he's wrong he gets all upset and continues coming up with more BS.
Don't think too much farang. It's done within 3 days before arrival or on arrival. You can't do it 1 year in advance and I have to laugh at those farang who plan their trips that far in advance.
So they're still allowing the use of paper forms? That's good. Hope they will allow them indefinitely. For land borders, I presume paper forms will remain the default option but they'll probably ask you if you've filled out the form already in advance.
Thai immigration uses helpers from the neighboring country, especially at the Cambodian and Burmese borders, so you'll be dealing with Cambodian/Burmese nationals wearing immigration shirts. They speak far better English than the Thais, one of the reason they're employed not to mention they are also used to help their nationals who may not speak Thai or English [or not well].
Yes but if arriving by land there probably won't be any machines available. Some land borders have only temporary facilities so you'd need to fill out the form on your device at the latest when you arrive before passing through the border or preferably the morning you depart your hotel in Laos, Cambodia, Malaysia or wherever.
You were lucky there were so few people. That border can get busy with Cambodian workers. Thais are rare except for casino punters as Thais don't like Cambodia so it's always Cambodians who are in the vast majority of those crossing the border.