Feb 10, 2016 - 12:17 PM
in reply to johnhalf
Chiasso is where validity of the Swiss Travel Pass starts, and as far as I know all trains stop there (see the timetable). There's no need to get off the train there, but you can if you like. Normally you buy the pass and the ticket for the Italian leg in advance and stay seated.
If the pass needs to be validated at all, it can be done on the train (see here). If you buy the pass through www.swissrailways.com/ en they'll e-mail it to you and you simply print it at home. You can fill out the blank fields manually and you're ready to go. No further validation needed. For more purchase options, please see the links in my previous post.