Doesn't it all depend on how you look/present yourself, if you smile? If they take exception to you for whatever reason, (this is customs too the world over) they aren't going to be nice to you, because they love the power trip.
they do ask for your passport and take a photo. I just got mine at 7-11. 7 days data SIM. Then you download the app and buy a plan. Didn't change my number still have access to what'sapp, other apps, banking etc.
don't these schools have holidays? My daughter is learning Thai and looking to get an Ed visa, but if it means she can't visit us for Christmas or Easter that's a no go!!