Padmanabh Swami is known as King Padmanabh before he took diksha and became a Tirthankar.

In Jain tradition, Padmanabh Swami is the 6th Tirthankar of the future Utsarpini kaal. Before renunciation, he is described as a king named Padmanabh.

If you mean a specific title like “king of which city/region,” then sorry, I can only provide information that is clearly established within Jain tradition.