I imagine Thailand - just like the UK, Germany, etc - charges them with breaking a specific law, and the general public thinks nothing of it.
No they don't. There are some complete nutters in Western politics who have never been jailed and are not likely to be. They are more likely to face the consequences of any law breaking where the "ruling classes" wouldn't and are also far more likely to be under scrutiny by someone looking for a reason to justify the prosecution but they do need to actually commit the crime.
Absolute Monarchies seem to be much better at getting things done because they can avoid the committees but Western Democracicies overall are much more reasonable and tolerant of dissent, even if not by as much as is claimed.
3000 security personnel arrested members of a fringe German monarchist group, because of their cough credible threat to overthrow the federal republic.
This "political opposition", no matter what you think of them.
I'm pointing out that it's not a completely foreign concept, and easy to understand if you slot in a different value system.
Understanding something isn't condoning it.