Participant(e) anonyme Where did you apply BTW? If their request for further documents mentioned specifically "a letter stating that you can work remotely", then I guess you should be fine if your letter says something along the lines of "work remotely from anywhere in the world". If it mentioned specifically "a letter stating that you can work remotely from Thailand", then don't risk it, get a letter mentioning Thailand.
Participant(e) anonyme Yes, way to go. Does not look bad at all.
If you can figure out anything else you could show to them, enclose it. Maybe proof of finances that do not qualify for the 500K THB (brokerage account, etc.).
They could have sent a standard description. Write a cover letter in which you explain what you've just explained in your post. Send the pay slip you already have. Try to think of something you might have, to show on top of that. You haven't sent the extra letter written by the CEO of your company yet, have you?
Not sure about "The photos must show the date and time they were taken" though. You won't be able to have metadata imported into the final PDF. If they had written day only, I would have suggested to buy a newspaper and make pictures of all pages on it. No idea how you could prove at what time they were taken...
Participant(e) anonyme Not all embassies have such a list. They usually publish it on their website. You can go to any translation office I suppose, and ask if they provide certified translations from the source language into English or Thai.