Are you in, or travelling from, one of the countries that are flagged for yellow fever? If not, then you don't put anything because it's irrelevant to you. Make sure you're on the Thai official page for the free arrival card.
I do. But as I've said I don't use an app. Not sure why you have theory that thinks people "don't understand", just because they don't use an app. Your arrogance speaks volumes about the sort of person you are.