This illusionist seems to be sitting on an invisible chair. There seem to be no "invisible" strings to support him. He is no way "connected" to his suitcase standing near to him. The same trick was observed on the Canary Islands and the man there had no suitcase. He arrived on his bike, and sat down just like that. For a very long time, just every now and then moving a bit into a slightly different positions as to make it more confortable. But he seems to avoid to get up in the mid of the public as to prove that he is not supported by anything...all by all very strange to see, so no wonder the crowd in Basel was gathering around him...

Below you see also the picturs from the similar act as spotted on the Canary Islands.