I am currently in Thailand on a non I'm o visa ( Thai spouse ) but I need to return to the uk while I am out of Thailand my visa will expire if I returned on a tourist visa would I be able to convert this to a non I'm oa visa in Bangkok 

What is the exact type of non-o visa that you have now? Is it a single entry or multiple entry. Or is actually one year extension of stay you applied for at immigration?

One option that you might have is to apply for a 60 day extension of your current permit to stay and get a re-entry permit to keep the remainder of it valid when you return.

You can only apply for a OA visa in the the Thai embassy in London.

Best to get a single entry non-o visa based upon marriage instead of a tourist visa while you are in the UK. Then apply for a extension of stay based upon retirement at immigration during the last 30 days of the 90 day entry from it.

UJ sums up your options perfectly, but more concrete advice could be given if you confirm the type of visa you have, when it expires, when your current permission to stay expires, and the dates of your trip to the UK.

 

It would be possible to do a conversion (get a non 'O visa/entry) in Bangkok, but it requires two visits plus a third to apply for the 1 year extension of stay (it's not an "oa visa").

 

If you can't keep the entry from your current non 'O' alive you are better off getting a new non 'O' in the UK. It is easily obtained with a copy of your marriage certificate and copies of your wife's ID and house registration book (Tabien Baan). It can be applied for by post from the London Embassy.