Serious question, since i am about to buy my teacher's wardrobe : Teacher Trousers should preferably be with creases ? Or is this considered to be over the top ?

I have worked at some pretty anal schools - as far as dress code is concerned - and I have never heard anyone mention that

Doubt anyone will care, but creases do look better, imo.

might sound daft but who wears trousers without creases? Jeans yes but proper trousers?

Every pair of long 'dress' trousers has creases, and every Thai laundress we've ever used presses creases into them. I've never heard this discussed. Thais think you should dress "sharp" but they're not that picky. Unless you're earning 1,500 baht per hour in the best office in Bangkok to teach corporate executives who all wear $1,500 suits, just wear what the laundress pressed, 2 or 3 times, and send it back to the laundry.

It depends where you work. If you work in Thammassat University, you'd get by a polo shirt, smart shoes and many different types of trousers.

If you are doing corporate work you nee a tie, good shirt and trousers.

If you teach 'anuban' you might get away with anything.

Prathom/Matyom seem to the very fussy.

might sound daft but who wears trousers without creases? Jeans yes but proper trousers?

I think he is referring to the "Dockers" style, casual pants, which you don't crease.

Serious question, since i am about to buy my teacher's wardrobe : Teacher Trousers should preferably be with creases ? Or is this considered to be over the top ?

Preferably creases, yes. Noboby would criticize you for looking too smart in Thailand.