Man now this is a dish I'd love to try making. I wonder how you make sure clay is food safe though...
While I don't have a confirmed answer, I have some hypotheses.
Baking the clay requires a very high temperature, which should be enough to kill off any bacteria. Secondly, the chicken itself is wrapped in lotus leaves before being covered in clay. The leaves are not eaten with the dish, so they act as another protective layer between the chicken and the clay.