:ghostface:

I am a 30 y/o Australian with a Thai wife.

I have a non immigrant O visa.

How do I change this to a non immigrant B visa?

(as I want to work in Bangkok)

Cheers...

You have to travel out to the nearest Thai Consulate or Embassy and apply for a NON-B. http://www.thaivisa.com/275.0.html

You will need a letter from your employer, example letter here:

http://www.thaivisa.com/332.0.html

To change a NON-O to a NON-B at the Immigration is (nearly) impossible, and I wouldn't recommend that route.

Do you really need to change your visa class?  Believe any non immigrant visa can be issued a work permit if you are in the country.  But have not 'been there, done that' so will leave final word to someone who has more knowledge.

To obtain a Work permit on a NON-O is possible. Labour Department doesn't care. The problems comes later when you want to make a yearly extension at the Immigration for the purpose of working... Ooops, then the visa class is wrong and any application for one year extension will be rejected. Square one again = travel out and get a new NON-B, and, in worst case, re-apply form the work permit...

Labour Department and Immigration does not speak so well with each others... ???

a yearly extension at the Immigration for the purpose of working.

But now he has a job and money in the bank why can't he request extension as support for his Thai wife (class "O" visa).  Don't see any reason he would have to change visa class as long as he keep the wife happy.