There is a Thai teacher in my school who many students refer to as mæ̀ (which I suppose is the same as แม่ and translates to "mom" or "mommy")

The first few times this happened I thought the students were actually her daughters, but she is only - at most - in her late 20's herself. Clearly not old enough to have children in their late teens. "Older sister" would be more fitting. Over the course of the year I've seen many dozens of students (boys and girls both) refer to her in this way.

This would creep me the heck out if I were in a school back home, although I could possibly understand small children seeing a teacher as a parent-figure, but these are teenagers! I've chalked it up to students trying to cozy up to a teacher perhaps for favoritism - mainly because there are other female teachers (who also happen to be older and hold higher office) who don't get called mommy by the students. As far as I know, this teacher has no particularly high status in the department. She's not a department head or anything.

Has anyone else noticed this at their schools?

Perhaps it is her name? Or it could be an inside joke. Personally, I wouldn't worry about such things. To be honest it really isn't your business and you would be better off not judging or thinking about it. I definitely wouldn't talk about it with other teachers.

I'm neither worried nor judging (at least openly). Just curious.

No it's not her name. At least that's not what the other teachers and I call her. And now that you mention it, I don't think I've ever heard a student call her "Teacher [name]" like they do the rest of us.

Probably she is a caring and loving person, so the students associate her as a mother figure.

Nothing, wrong with this OP, I wish all the teachers in Thailand inspire love and care for their pupils.

Then may be the school would be a better place for them to be.

This translates into English as "Mum" or "Mother".

It's normal in Indonesia to call an older teacher 'bu' or 'ibu' which means 'mum' or 'mother'..

But for younger teachers it's normally 'non" or 'nonya' which means 'miss', same as in English speaking schools.

Do the students in Thailand use the equivalent of 'miss'?

Does she look similar?

"This would creep me the heck out if I were in a school back home"

That is the problem. You are in a different world.

Live with it.

We had a strange Thai English teacher at my former school and her trick was to do something similar.

Whoever had to work for her, usually Rajabhat students who wanted to become teachers, she always approached them in a way where they couldn't say no.

Her "story" was that she always wanted to have a daughter, then she told them if it would be okay to call her Mae, while she called them Noo, or Luuck.

But she also did that to students and those who said yes, were really screwed.....

A brilliant way, if you want some Thai kids to do everything for you. --

Its quite normal, I have some workers who calls a manager "Mae" in my factory.