Has anyone seen the episode of Farscape where Rygel goes back to his planet with Chiana and Ka Jothee? I can´t find it anywhere.
There is no such episode. Dealing with multiple Hynerian puppets was deemed to be too much of a technical challenge, so more than two at a time were never attempted.
However, in the very first issue of the Farscape comic book series, those three characters, Rygel, Chiana, and Jothee indeed do travel to Hyneria to try to get Rygel his throne back. (The story arc continues for three more issues after that.) That must be what you are thinking of.