Whether this answer is acceptable to you will depend on how you define "advanced race," "fantasy," and "beings of light," but here goes...
As most modern stories which talk about "beings of light" tend to do so with some sort of religious or spiritual overtone, it is probably no surprise that the concept would have originated in the realm of religion and spirituality.
Stories of people turning into angels, demons, ghosts, gods, or other spirtual beings have been around for millennia, and in many cases these types of spirit-beings (especially angels and gods) are portrayed as "beings of light".
A few examples I could find, in roughly reverse chronological order:
- 1843 - A Christmas Carol
- ~500 AD - Christian artwork begins to show the ressurected Jesus as a "being of light"
- 61-115 AD - An Ancient Ghost Story by Pliny the Younger
- ~500 BC - Greek mythology has the myth of the phoenix, which dies, to be regenerated as the sun
- ??? - By some accounts (1) at least some segments of Hindusm hold that god-like or angelic devas may have been humans in past lives
- 2494 BC - The Egyptian god Ra was the sun, or represented by the sun, although he was not, to my knowledge, believed to have been a lesser person/being previously
- 2780 BC - The Egyptian god Atum, also represented by the sun
- 3000? BC - Egyptians believed the deceased Pharoahs would become gods after death and "ascend to the sky and dwell among the stars"
I think this last one is both the oldest I can find, and the closest match to your description, leaving only the question of how you define an "advanced race."