Foreigners usually pay higher fare on int'l lines than Slovak residents. Antwerpen, Bochum, Brno, Brussel, Breclav, Budapest, Ceske Budejovice, Dortmund, Duisburg, Dusseldorf, Essen, Frankfurt, Gyor, Hainburg, Hradec Kralove, Jindrichuv Hradec, Kaposvar, Katowice, Kittsee, Koln, Krakow, Liege, Lignano, London, Mosonmagyarovar, Munchen, Nurnberg, Ostrava, Paris, Plovdiv, Praha, Prostejov, Reims, Rzeszow, Schwechat, Sofia, Sopron, St. Gallen, Strassbourg, Svitavy, Szombathely, Thessaloniky, Trebon, Udine, Venezia, Vyskov, Wien, Znojmo, Zurich. They operate only few lines, but usually they are more comfortable than SAD buses. They use electronic or mechanic counters. You can use buses, trolleybuses and trams.
Tickets are avaliable at the newsagents, in hotels or in machines at most stops.
Tickets from various towns are not interchangeable. They stop only on request. Some cities don't use ticket-punching system. Usually tickets are sold by the driver. You have to use only front door to enter in this case.