Stop fishing and just go with your actual situation then you won't have a problem. If you can't show earnings you can't use workation. If you use soft power you still can be asked for evidence as to how you will support yourself. Bottom line is no matter what you do you are likely going to have to show income. They want 3 months of statements but only the final month needs 500k
I'm not sure it's even possible to cancel a visa. But you can convert a DTV to another type of visa at an immigration office inside Thailand. You will need paperwork from your employer to make the change
if you are over 50 it makes sense to get either a Non-O or a Non-OA visa particularly as you own a condo. Personally I'd get the Non-O but the choice is yours
You need to have a job for the LTR option you propose plus meet the other requirements. You can't work in Thailand on a DTV. Seems to me your best option is to find another job that will support a Non-B and Work Permit
correct. He know lives in Thailand, he is just another tourist and can only stay for 180 days at a time, he may well lose his bank account due to being a tourist, he can no longer get a 5 year driving licence etc.