You can use (re)merci with either pour or de with abstract nouns. (Re)merci pour is the only expression for standard use with nouns for physical things. Therefore either is fine with “aide”.
As pour can be used with any noun, it is a safer bet for non-native speakers (we don’t want to ‘merci du cadeau’ by accident). If you’re confident, you can use de with abstract nouns and reserve pour for “physical “ nouns.
The usage is different with infinitives where merci de is required.
So, pour works for all nouns, de works with infinitives including the infinitif passé.
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