Well, bit of a spoiler alert here, but you can google a reveal fairly easily, so I don't feel too guilty :-)
Notice the long sleeves and long skirt on his robe ? It hides a simple metal structure which goes up his sleeve, down his arm, and under his derriere to sit on.
In the street, his stick (which will have a metal core) will attach into some solid structure. On stage, he'll have collaborated with AGT to have a secured hole on stage, for the stick to fix into.
I've seen a BBC article, video-ing the same trick in India, then showing the Swami demonstrating the metal structure.
The clever bit is the collaboration to deceive - either here with AGT, to prepare the anchoring structure - or on TV, to falsify the image or prepare another concealed anchoring structure.
The guy's delivery is very skilled though - kudos to him :-)
Could there be any greater conceit, than for someone to believe that the universe has to be simple enough for them to be able to understand it ?