Hi,

I will be teaching a course in a university in Thailand for about three months. I will get paid by the university. During my visit I might visit the neighboring countries for a short period as well. What kind of visa should I apply for? Many thanks in advance for any advice you might be able to provide.

You will need a either a Non-imm B or Type O and in addtion you need a work permit, The university you are working for will be able to advise the procedure...they need to supply with all the docs, take these to the Thai emabassy closest to you and your passport, believe also you need the a receipt to prove the application for the work permit has been made as well these days

There is no such thing as a working visa in Thailand, and if working whether paid or unpaid you need a work permit...