How many months can I extend my Non-O visa in Thailand without 400,000 Baht as I am married?

For the OP, you came in on a type O short term visa for 90 days. There is another option, and actually the correct option, you should and can do. You meet the first requirement in applying for the long term type O/Thai wife marriage visa extension after you got to Thailand. You can not apply for this long term extension outside of Thailand. Within these 90 days go to immigration with your Thai wife, and your marriage certificates, there are two, and use form Tm7 and apply for your long term Type O Thai wife extension. If they accept it, and they will with your wife there, and your marriage certificates, you will get another 90 day extension, that gives you enough time to get all the documents you need, and meet the first application financial requirements, that incidentally require bt400k in a Thai bank account in your name only for at least 2 months, OR, deposits coming from overseas of at least bt40k a month for at least 2 months into your bank account this first time. After this first extension you will need bt400k in your bank for at least 3 months, OR deposits of at least bt40k for all of the last 12 months, and they do not average the amounts anymore like they used to, so you can not miss a month, and the next month deposit double. It has to be above bt40k every month. When you go to get this extension with your wife, they will give you a list of all the documents you need to get to complete this application process. At the very least, this is a way you can extend your current type O 90 day visa for another 90 days, for bt1900.

David Broadfoot there is no 'regular" 30 days extension for Non-O entry..