Either is fine. What’s the context?

The correct phrase is "sing high praise of." Here's why: "Sing high praise of" is the standard idiom. It means to speak very positively or enthusiastically about someone or something. Example: "The critics sang high praise of the actor's performance." "Sing high praise for" is less common and not widely accepted as standard usage. While it might occasionally appear in informal contexts, "sing high praise of" is the preferred form. If you're unsure, you can also use alternatives like: "Offer high praise for" "Speak highly of"

Praise "of" something praises the thing itself. Praise "for" something praises on behalf of the thing. For example, suppose you are praising a very fine automobile. You speak about how smoothly it rides, and how comfortable it is. If that is your sole purpose, to explain how good it is, then that is "praise of" the automobile. But, now suppose you explain the same information to a friend who is searching for an automobile to purchase. You say the exact same things but your goal is to convince your friend that that automobile would be a good choice. That would be "praise for" the automobile because your aim is not to praise the automobile itself but to argue on behalf of the automobile.