"half of the people were on visa runs and about half of them were in the same situation as him", then it is no wonder that Immigration was denying so many people. So many people that were clearly not genuine tourists, and I'm not surprised that they would be much more strict. Interesting that the minute Cambodia opens, there is such a mad rush to do visa runs there. Probably wasn't wise to think that immigration wouldn't notice.
Why are you trying to sound like I made any judgement about whether he should be allowed in? All I did was say why immigration would have denied him. He's clearly not a tourist, that's all I am saying, and he tried to get away with entering by an entry intended for short-term tourists. He didn't qualify and is hardly the first person to get in trouble with immigration for this. As I see the moderators of this forum always repeat: "get the right visa for your intended purpose and length of stay." Who said anything about wanting him to spend his money here?
I think you kind of answered yourself why they would deny him. He's stayed in the country for 2 years and thought he could leave on a visa run and be allowed back in when he clearly isn't a tourist.
Assuming you don't mean Covid vaccines, you really don't need anything else. I don't understand why people think Thailand is some exotic place when most people are just heading to Bangkok or Phuket and would never think to ask the same question if they were going to Tokyo or Rome or any other developed metropolis.