Do I need to bring passport?

Yes you do need to bring your passport. The number of nights you stay in Italy has nothing to do with it.

Yes you should always carry it with you when you travel regardless of where you are going or how long.

To echo what the others have already said, yes you definetly need to bring your passport!

Thank you for your prompt reply 😀

Yes, you always need to carry a passport whenever you are crossing borders, and at all times in some countries (Germany yes, not sure about Italy). Even if they don't check you at the border 99.99% of the time, any policeman can ask you for ID at any time.

As a legal foreign resident you will have a Swiss Aufenthaltsbewilligung (Residence permit) which you carry around all the time in Switzerland as you legal ID. As a non Schengen/EU citizen you need to carry this as well as your passport whenever you are outside Switzerland. This Aufenthaltsbewilligung is your proof you are legally in Schengen and have permission to stay past the 90 day limit. Without this, police could question why your passport does not have an entry stamp within the last 90 days.
The requirement to carry your Aufenthaltsbewilligung outside Switzerland does not apply to EU/Schengen citizens, because the 90-day limit does not apply to them. But, I still carry mine, as it is a legal requirement to carry it in Switzerland.

That said, you will probably never be asked for either document, but I have read the Grenzwache (Border Guards) are doing increased spot checks on trains coming from Italy, due to the number of illegal immigrants trying to sneak across the border.

Yes, you need to have your passport on you.

Regarding Chris' comment:

That said, you will probably never be asked for either document, but I have read the Grenzwache (Border Guards) are doing increased spot checks on trains coming from Italy, due to the number of illegal immigrants trying to sneak across the border.

When we crossed the Swiss border (from France), the train stoppep & the Border Guards checked everyones passports or IDs, so you may have to do the same when you cross the border.

Priscilla, you got unlucky. The Grenzwache don't want to waste their time on the locals who cross the border in their thousands every day by bus, train, car, bicycle and on foot. But they appear to know what methods of transport people who are not regular border crossers would use, where and when. If you look like you have crossed the border hundreds of times, and are just going shopping or going to work, you will never get stopped. people who look like they have never crossed that border before are targets.

Only slightly related, but -- when we came through CDG this week, there was a line at the EU passport checkpoint, which is usually just a walk-through gate. Passports were indeed being checked. (We saw it from our viewpoint in the "all other" line.)

Regarding to Chris reply, I was in Switzerland for 29 days not past 90 days yet, so I do need to bring B permit? I'm looking forward to getting your reply 😀

yonpwintphyu, so you have only just got here. I hope you are enjoying yourself and the late summer we are having (30°C predicted for next week, in September!).
If you will be back from Italy within 90 days of your arrival in the Schengen Area (and the stamp in your passport), then you probably don't need to carry your B permit in Italy. But, you need to carry it all the time you are in Switzerland (Swiss law), so you need to take it with you anyway.

You will most likely have to show your passport at your hotel in Milan. I was in Italy in May, stayed in 6 places (including one night in Milan), and had to provide my passport in each place.

Chris,

We were unlucky? I suppose so.
We were staying in Chamonix in late May & took the train to Martigny one day, that's when the Border Guards got on the train & checked everyone's passports & IDs.
There were only a few people on the train. I recall a man sitting on the seat 2 rows in front of us, & he was questioned at length but I didn't quite understand why.

Anyway, I always carry my passport in my money belt when traveling abroad.

You always have to show your passport when you check into hotels or apartments in Italy. They will take down your information and forward it to the police. This is the law so don't be alarmed when they ask for your passport. You must carry it with you at all times while in Italy.

Donna

In my experience the most scrutiny I have ever received is crossing the Swiss/Italian border in either direction. Has been this way for the past 15 years at least.