When you get the 1 year marriage extension then you ask for a re-entry permit at the same time - or else at the airport when you leave. That is my understanding, others with more knowledge than me can confirm. You would also need a work permit in Thailand if you want to work and that is only granted for certain types of work.
I think you will have to be in Thailand near the anniversary of the extension every year to extend it again. That may be a problem if you can't control the timing of your offshore work.
If you are flush with cash, the Thailand Elite Visa could be an option for you. It is a fee so the money is gone, but it may give you the flexibility you need.