It's well known that George Lucas took many of is ideas for the Jedi and the Force (among other things) from elements of Eastern religions. (I've seen pages, for example, that talk about how much of Star Wars meshes with Buddhist beliefs and other pages that say the same about Hindu beliefs.) Both of these religions include reincarnation.
Force ghosts show us that there's a sense of a durability of the soul, especially since Qui-Gon went to the Netherworld of the Force, but was still able to come back, which tells us that even in that Netherworld, the soul can maintain integrity. It's said that eventually Force ghosts have to leave and go to the Netherworld of the Force, too. Yoda was seen there, training two people.
While the belief is that non-Force sensitives become one with the Force on death (which is like the Buddhist belief of Nirvana), it seems that, in spite of Qui-Gon's beliefs, souls do still have a sense of self in the Netherworld.
Since this establishes the concept of souls continuing to exist after death, is there anything in Star Wars that indicates a soul that has been a Force ghost or has been in the Netherworld of the Force (or elsewhere) has come back in another body?