The gym needs to be registered both as a business entity and also a sports entity.
Tiger eye in Bangkok has done loads of these. Just do a search in the group
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If your gym can't provide one then go to a gym you can at least drop into once. This is why a gym in Bangkok will be a good option as almost everyone is going to fly into Bangkok.
Also, tiger eye doesn't force you to sign up for long courses. You have regular options as well