Hello Nouphoupuemb83
Unfortunately Frankfurt is not in Switzerland and you must buy tickets from this city to Basel Bad Bf (German station of Basel). You pass will be valid later.
If you want Saver or Supersaver Tickets, buy them on bahn.de, but not if you arrive at the airport. Such discounted tickets will be lost if your flight is late and you miss the selected train.
Kind Regards
Danhiel