Go to the Thaiembassy website. It will route you to LA or DC. Determine the VISA you wish to get and proceed to enter data, take pictures and Pay. Then in about a week it should be ready for you.
I believe what the last member was trying to convey is a VISA is different than a “Extension of Stay.” If you had a 1 year multi-entry VISA from your Home, going to the border would only work to serve for the 90 day requirment to leave the country, and return. This is Only capable on a Multi-entry type VISA. The only way I am aware of getting an extension of stay is to have a long term multi-entry VISA from your homes Thai embassy, first. Then apply for one of the in country plans. I hope this clarifies a little.
Did you have to get a “Foreign Insurance Certificate”? Sorry for the barrage of questions, but as usual, I’m overwhelmed by the lack of clear instructions from Immigration. Thank you for your discourse.