Julinhio Gaichet. That's the maximum allowed for studying Thai language. A person can possibly switch to a different study course. The only ED visa long term is university degree
Stella Labang. You'll need to get a firm plan on what you actually want to do, work or study, and as George has said you definitely need to be married as you will have to provide a marriage certificate which has been certified as authentic. Defacto relationships mean totally zero in Thailand. I don't believe you can get an ED overseas at the moment, but you can speak with schools (many of which have a dedicated visa service - a defacto visa agent, except they are completely legal) you can find one in the area you plan to live. The school can arrange the visa and the cost is inclusive in your course fees. Once you've done this and converted your visa, your spouse can then apply for an extension based on being married to a foreigner on an ED visa. I concur with George, the man you want to speak to is Tod Daniels. I'm on retirement visa having had a non-B years ago, but my knowledge of switching to ED with trailing spouse is too limited to give you sound advice