IR trains do not offer seat reservation, only IC/EC/ICE, and PE trains.
Please note: in Switzerland, train tickets never include neither a seat reservation nor a guaranteed seat. All you pay is for the transportation from A to B to C.
In Switzerland, trains are mass transit like suburban trains elsewhere: you buy a ticket, you get on the next train and take a free seat. In the unlikely event the train is fully booked, you might have to stand in the aisle or on platforms.
If you want to reserve a seat, take the IC1at 12:04 or, even better, the IC8 at 12:32 direct to Visp without change of trains in Bern.