What are the steps to obtain a DTV visa for an older couple in Thailand, including cooking schools and application process?

If you do a quick search in the group, both Vietnam and Jakarta seem to be the go to embassies in the area. The biggest issue will be getting a course that is accepted, some aren't so you'll need to pick one that's "real". You would both have to register and pay for the course so it would be cheaper to just have one on the course and other as a dependent, assuming you can provide the marriage license, etc. That would mean you'd need a longer stay where you choose as the main DTV holder would have to apply first and once approved, then the dependant would apply.