Hi I have a Non Imm '0" multiple entry visa ( Married to a Thai citizen ) which is due to run out at the end of July I wanted to know if it was possible to get a 3 month extension? I have been told that all I need to do is leave the country and reenter before my visa runs out and I will be granted one more entry period ( 3 months ) before having to seek a new visa from within my own country. Thank you and I apologize if this has been asked many times before.

You can leave and re-enter up to the day before your visa runs out and get another 90 day entry. This would not be getting an extension. It is just using your visa and getting the most out of it you can.

You also could go to immigration and get a 60 day extension (1900 baht) to visit your wife if you just want to stay a little longer.

Thank you very much I appreciate your time and effort in answering my question...