Yeah, I had the same concern.
My Embassy said for cooking class, I need proof that I will be attending FOR AT LEAST 3 MONTHS.
I dont want to ask them a million questions to annoy them, but I am assuming this applies for every extension.
Then, how much will this be enforced? For years, people did not attend classes on ED Visas and got away with it.
But would you risk having the DTV revoked?
Do you really want to take Thai cooking for 3 months?
Another major issue ... does it have to be full-time?
I may try to get a cooking school to give me a letter, but I would only take 1 hour class per week for 3 months. Or even 1 year. Who cares if it's only 1 hour per week?
But full time or 20 hours a week of cooking is ridiculous to get a visa.