@Aurélien ********
I have yet to have the hard time that you talk about in Thailand although I have been here for only a year with that said I don't anticipate any issues either. I dress properly I act respectfully at all times but especially at immigration, and the only problem is I encounter are due to my inability to speak Thai language.
maybe you have had other problems here but even so I think it is their country, and can do what they want with it.