How to search in other languages using an on-screen keyboard
If you use a language that requires special characters like Arabic, Greek, Thai, use the on-screen keyboard to enter precise search terms in YouTube.
The on-screen keyboard is only available for certain languages.
Click the keyboard 
in the YouTube search bar to display the keyboard. Move it around by clicking it and dragging it.
To use the keyboard, click the keyboard with your mouse, or enter the corresponding key on your physical keyboard (not all physical keyboards are compatible).
To display more characters, try clicking Alt+Ctrl and the Up arrow key on the keyboard.