What documents do I need for a Marriage Visa in Thailand, and is document 6.3 necessary?

If you are female marrying a Thai man, and getting married, and registered in Thailand, there are documents you don't need for your type O extension. If you get married in Thailand you need part 6.1.3 in order to get married, and then you only need part 6.1.1, and 6.1.2 for your visa extension. It is best to actually go to immigration as they have a handout list of what you actually need, and it changes in some respects almost yearly. Also, always go with your husband for anything visa extension related. They always want to see both of you together. Keep copies of all the documents because in your case the only change in following years are the pictures. If you were a male married to a Thai female there would be bank letters needed, but as a female you don't need those.