Hello @chongmin
Not for regular trains (IC, IR, RE, S, R). These trains are mass transit: you show up at the station, you check for the next departure, and get on the desired train / service.
If you wish to take certain panorama trains (PE), however, such as the Glacier Express, a seat reservation is required. Check the legend on the timetable to know if a train needs seat reservation.
Best regards,
Roland
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