Kim, 21, had won the belt in Rise of Kings last year but injury prevented him from defending it in recent One FC tournaments.
In his stead, Fernandes was established as the interim champion after the 33-year-old dismantled Koetsu Okazaki with consummate ease in Manila's Rise to Power event.
The Brazilian, billed as one of the top-ranked bantamweight fighters in the world, is a former Dream featherweight champion and is currently on a six-match winning streak. He will face the much-younger Kim who has seven wins to his name from 11 fights over the past three years.
The duo will headline 'Total Domination' in October and the organisers have announced that the tournament will also mark the second appearance of a female MMA fighter inside a One FC cage.
Sherilyn Lim, representing Singapore's Fight G, has been chosen as one of the fighters on the roster with her opponent on October 18 expected to be announced in the coming weeks.
Before arriving in Singapore, One FC will have to complete Champions & Warriors, which takes place in Jakarta on September 13.
The event will feature fighters from Malaysia, Indonesia, Pakistan, Japan and the United States and is headlined by a flyweight contest between Andrew Leone and Shinichi Kojima.