Whatever you do make sure you get the old visa cancelled with a stamp in your passport.
This means, cancel the work permit first, get the little receipt they give you and take it to the immigration office that did the original visa for you.
I had massive issues with this that nearly got me 'technically' blacklisted just because the work permit had been cancelled, the visa had expired but I hadn't got a tiny little stamp at immigration to cancel the visa (even though it had expired and a new VOA stamp had been given from a border run).
Work permit visa was issued in Phuket, and Pattaya could have helped but chose not to (because they don't have to and are not supposed to)... It was an absolute nightmare and ended up being expensive to fix too.