Special beats general, almost always
A special power names the transaction, the property or the account and the limits of the authority. It is safer for you and more readily accepted by registrars and banks, both of which are wary of open-ended documents. A general power is a large amount of trust in written form and should be a deliberate decision rather than a convenience.
Many offices insist on their own form
The Land Office among others requires its prescribed form, completed exactly, describing the transaction in the terms it uses. Your own carefully drafted wording, however clear, may simply not be accepted. This is the single most common reason a power of attorney fails on the day it is needed.
Signed abroad? Plan the chain before signing
A power of attorney executed overseas usually has to be certified where you sign it and then legalised at the Thai embassy there before a Thai authority will act on it. Doing this out of order — or discovering the requirement afterwards — means signing again from the other side of the world, and the transaction loses its date.
Revoking it properly
Acts within the written scope generally bind you toward third parties who dealt in good faith, whatever was agreed privately. Revocation therefore has to be written and — critically — notified to the attorney-in-fact and to every office or bank holding a copy. A revocation nobody has been told about protects nobody.