Do I need to enter Thailand with a Non-O visa to apply for a married visa, or can I apply for both while in Thailand?

@Tin ***

then your only easy option is to come in on a tourist visa, or a visa exempt stamp (the tourist visa is the best), immediately get legally married, and it takes time as you need one important document from your embassy, a right to marry document stating that you are not currently married, and your status, divorced, single never married, or widowed. If you are divorced then you need copies of your divorce papers, and a copy of the death certificate if widowed. Most just check single as it is too hard for them to check. Then this document must be translated into Thai, and the ministry of foreign affairs must put their stamp on it certifying that it is an accurate translation. Without this document, and translated, you can't get married. Once you have that, then the next step is to go to your local Amphur and make an appointment to get married. It is done at their desk, and not a big ceremony, but, you do need two witnesses. We used the couple in the queue behind us, and they used us.

Then as soon as you have these two documents, the marriage certificate, and the registration, go to immigration, with your wife (alway go with your wife, except for your 90 day reports), and show them those two documents (on a side note get full color copies made of them), your wife's ID card, and your passport, with copies, and you'll get a 90 day type O extension, giving you enough time to get everything for your one year extension. They will give you a list of everything you need. The first year can be difficult, but, as long as you keep copies of everything, the following years all you need is new bank letters, and new pictures, if nothing else has changed. Good luck, and have fun.

@Kool ******

The 4 categories of the Non Imm O are marriage, over 50(retirement), dependancy and volunteering.