I work with dozens of Thais daily, and interact with hundreds of Thais professionally in a year.
Making change is not always about posters and shouting and forcing your opinion on people.
Sometimes it is about quiet conversation, and a small comment.
"wow, i saw that ad, what do you think about that?"
Hi-sos can hit people with no consequences?
What do you think about that?
No need to state a position. Change is a slow process, that come come from a small event.
We don't have to shout and scream. Sometimes we can whisper.