Question: I'd like to ask if there's a way to make chrome extension ONLY activated in incognito mode.

I only want the extension activated in incognito mode and disabled in normal browsing. 

I do hope there's a way and thanks in advance.

Answer: 
You can't do exactly this. 

Closest way is to create a separate Chrome Profile and install extensions there.
You can do this but for that you require Opera Browser. Activating Extensions Only in Incognito is not possible in Chrome, Switch to Opera.