There was a recent thread about this. DTV you can work remotely legally. Strictly speaking on Retirement you cannot. Less visits to Immigration Office with DTV. Money not tied up in a Thai Bank if doing capital option for the O. Costs can be debated but it depends how much you travel. Full 5 year O with multiple entry permit each year cost is
*****
currently. The DTV is 10k initial plus SP if that route plus border bounces for most. The "O" is a much more established visa and is "Owned" by immigration who also own entry and extensions for both. That could lead to a speculative area which I will leave for others.
My best pal is quite a senior Diplomat (Not Thai). I was telling him about the DTV. He was amazed about 2 things 1) That the MFA could create a visa and issue it without the interior depth. 2) That embassies do not have fill sight of the system and immigration history of all applicants.
Talk to the Plants and Herbs people on Whats-App. They are very responsive and will tell you where recent applicants have been successful. As for shorter courses there are currently no issues doing those and re-entering without further booked courses.
This is a difficult one. Was it the gym documentation the root cause or your finances or other issue? If the fault on your end the gym has no reason to refund.
Yes, if you leave on the "O" and do not have a re-entry permit it is basically cancelled. If you are applying for a DTV though I would point this out in a cover letter. The "Local Hire" initially reviewing your application at the Embassy you apply to will not likely know the nuances of all Thai visa types. PS: Why change now though? Can always get DTV towards end of "O"