Noted that it’s the extreme value I put in here to see the change. It seems like not only that it didn’t pick up the condition but also apply on every situation too. I’m not sure how to fix this.
The code you wrote only applies to variable fonts. Not for static instances.
You can add a “Add Feature” parameter in the darker instances with that pos rule (without the comments and conditions)
As far as I can tell this works for me. Except that in the last screenshot you are missing a ' after the maiTri-thai.narrow. And can you check if the maiTri-thai.narrow is actually substituted in by the time the make feature is applied?
If you can’t figure it out, you can send me the file (e.g. in a private message).