Hi! If I apply for the dtv for a course/activity like muay thai or cooking course, is the visa still valid even beyond the course duration or will I be required to leave Thailand?

Also, if you are legally common law in another country, are you able to bring your dependant with you on the DTV Visa, or will you need to be legally married in order for your dependants to accompany you?

Hope someone can help clarify these items!