BrightCranberry5804 In the first case you were dealing with incompetent embassy staff; in the second, the information you have is incorrect.

If for any reason you are not satisfied with my comment, you can pay a consultation fee of 5,000 THB and I will set out all the applicable regulations for this visa in your situation. All of this is clearly described and documented.

You already have the information you need. What you choose to do with it is your decision.

You don’t need to cancel your DTV separately in advance anywhere. In practice, you have two options: either get a Non-B visa abroad and enter Thailand with that, or enter Thailand on your DTV and then change your visa type to Non-B through Immigration in Thailand.

The message describes in detail where to get a list of these documents.

It's a good company, I can confirm. Their services are relatively inexpensive. For example, to obtain a Tax ID from the tax department, they only asked for 10,000 baht. But then I discovered it takes no more than 15 minutes, and I got the Tax ID myself.