@Karsten *******
the big difference is that on the type O extension based on Thai wife, you can get a work permit to work in Thailand. You can't do that on a DTV. Also, being married to a Thai, and working in Thailand, and paying your taxes for three years, plus other documents, etc, you have a route to apply for Thai citizenship after just three years, or get permanent residency, something you can't do on the DTV. A type O based on marriage has it's advantages.