There is actually a way you can create thin text within Illustrator.
Convert the text to an outline by:

• Switch to the Selection tool and choose Type > Create Outlines.
• You can also use the keyboard command Ctrl+Shift+O (Windows) or Cmd+Shift+O(Mac).
• Select the text and right click > Create Outlines.
• After the text has been converted to outlines add a stroke in the stroke panel or Window > Stroke:

• Select `Align Stroke To Inside’:

• Select the outside paths of the text and delete.
• I would suggest after removing the original type path for you to kern the type.

A good video to watch about kerning is “Typography Tip To Help With Kerning” but you could adjust the kerning before converting the text to outlines.
I would also like to address this method is not ideal for body text and it should be reviewed with a fine tooth if you plan on using this for Serif Fonts. Especially look at the Ear, Terminal, Tail, and Bracket.