I am on an Extension of Stay based on work permit expiring August. I will be changing my job in July. Can anyone  assist to advise if I can use the new Work Permit to extend the stay or I need to go out of the country to get a new B visa.  In any case, I just want to stay in the country for the same purpose. 
Regards.

Isn't that just a case of changing job/work in the work permit book..?

You will get a new work permit. They cannot do anything with the old work permit.

 

If your new work can arrange all paper work you can do it in 1 day. If they cannot prepare all the paper work you need to leave the country and do a new non-b

 

Here i suggest you to get all documents from the new work. There are many examples around me that the thai embassy where you go may not give you a new tourist visa with the reason 'you stay in thailad too long'. Dont question the reason. This is what happened at least 4 of my friends. 

 

If you have to leave the country be careful with the date on your work termination letter from your work. That date is the last day of your work and your visa and your work permit. 

 

Good luck