Is it difficult to open a bank account in Koh Samui? 

Very difficult or impossible if you are here on a tourist visa, otherwise not difficult.

Try Kasikorn bank ! You'll  need a Thai friend to endorse you. It has worked for some

If you can open a bank account in Thailand depends for the biggest part on the fact if the branch manager like your white nose or not.

 

Yes all banks will request a long term visa.

No you don't need a work permit.

 

As I said, the decision is with the manager of the particular branch, because in Thailand everyone with just a little authority makes up his own rules/laws on the spot.

 

So because you get rejected in one branch of a certain bank doesn't mean you can't open an account in another branch of the same bank just a few hundred meters away.

A number of unhelpful juvenile posts removed.

Choengmon branch of the Bank of Ayudhya (Krungsri) was fairly relaxed a while back. I do not know the current status though.

It might be worth trying all the different bank branches in Central Festival, if only for the fact that they deal with a lot of foreigners.

It might improve your chances if you have a house paper, or residents certificate from immigration.