I couldn't find a solution. It seems like the .as file extension is registered in the system as "AppleSingle Archive". In iCloud Drive on OS X it has a file icon that is similar to a .zip file.
So it looks like iCloud Drive treats it as a file archive and doesn't allow it to be opened as a text file.
Ideas
So it looks like iCloud Drive treats it as a file archive and doesn't allow it to be opened as a text file.