Hello bubbletea
Yes, even visitors can use Easy Ride provided they have a means of payment registered.
However, for tourists it rarely makes sense to use Easy Ride, it might be too expensive without the Half Fare Card. There are better (more inexpensive) offers such as the Swiss Travel Pass, or regional passes such as Tell Pass, Berner Oberland Pass, or Jungfrau Pass, or Saver Day Passes (with or without the Half Fare Card).
Best regards,
Roland