I have a marriage visa which expires on the 17 September,  do I need to do the whole visa process again or can I extend my current visa for one more year?

No you can not extend for a new year....  Are you having an extension of stay, then it is another thing.

 

glegolo

Do you have a one year extension of stay based upon marriage you applied for at a immigration office or a multiple entry non-o visa applied for at a embassy or consulate?

If an extension of stay you can apply for another one without needing to get a new non-o visa.

Do you have a visa obtained abroad or do you have an extension of stay obtained at immigration in Thailand.

If you have an extension of stay you will have to apply again with the same paperwork as last year.

Yes you can extend your stay for 1 year. You will need 400K in your bank for at least 2 months before the date you apply, or a certified (by your embassy) income of at least 40K pm.

 

You can apply 30 days (45 at some offices) before your current permission to stay expires.

A baiting post and a reply to it have been removed.