Most people indulge in erotic massage in Basel when visiting a local brothel (Bordell or Puff in German). There are however a few spots if you’re not into full service but looking for an erotische Massage. Azamour (https://www.azamourbeauty.org/) at Gundeldingerstrasse 311 specializes in massage and minor cosmetic stuff like hair removal.
If tiny hands and Asian expertise is more down your alley then Thai Massage Palace (https://thaimassagepalace.ch/) at Dorfstrasse 121, is the place to go. An hour will set you down around €80, which is incredible cheap according to Swiss standards.