How many countries have you heard of? I've taught in 4 countries where this is common. We're not in the good ole US of A any more Frank.

Often there will be an assistant for classes where the students cannot speak the new language, or the students can speak enough and you all only speak the language being taught. If you speak their language to them, they stop trying to speak English and only speak their language. Yes it helps to know some phrases to control a classroom but it isn't completely necessary to speak the language of your students.

Because you don't speak Thai to your students

For anyone in the same situation. I took my tm30 to immigration, gave it and my passport to them, informed them that I had just returned from another province and they made me a new one on the spot. It took about 15 minutes and didn't cost anything.

Thanks a lot

Thanks for the information. I'm not sure if the hotel in Mae Hong Son registered me for my stay there. Do you know if it is possible for me to check at immigration if the tm30 I have is still valid?