I think the answer is obvious but if I apply for a new 'spouse' visa 1 month before the old one expires can I get re-entry permit and travel abroad within the 4 weeks before the expiry date of the old visa ?

Edited March 23, 201214 yr by Rob5060

If with 'spouse' visa you mean a one-year extension of stay and if you have or get a re-entry permit you can leave and re-enter Thailand without losing your extension, as long as you re-enter before the expiration of your re-entry permit, which will have the same expiration date as your current permission to stay.

When you apply for an extension of stay based on a Thai wife, you wil get an initial extension of stay for 30 days. Your re-entry permit will be valid for those 30 days, you have to be in Thailand when you need to collect your approval and final permisison to stay or lose your permission to stay .

Just to be sure I mean current visa expires 21 June , applying for new one about 22 May and possibly travelling 1st to 15th June

Just get a re-entry permit after getting the 30 day under review stamp and use that for your travel.