I want to search for let's say
*.doc from all my files in Google Drive but I want to exclude results from a certain folder let's say
old docs. What do I type in?
type "-foldername" this will exclude anything named foldername from the search results.
for more options check out search options page
What I test, this search all text document in your Drive.
It is what you need?
There is more operators which you can use in Drive (under plus with text "Advance search option"). https://support.google.com/drive/answer/2375114?hl=en
EDIT (after Eight Days of Malaise reaction): Filtering by folder name is not possible in GDrive. Maybe use desktop synchronization app and after that use Explorer searching or some utility.