Alright, its the moment of a bit of My LeGaL advice!!
Folk tales are what is known as 'common heritage', and all that is inside the common heritage can be used for derivated works. You can inspire on them to create your own story. That mean that you can create a comic strip, use characters in another stories, or re-do again the story in another media -those are called derivative works.
To every piece of art that is considered to belong to the 'common heritage' can be done this. For example, Disney did most of their animated movies with books or stories that where inside the common heritage, and gave them a little twist to make them their own. The little mermaid, its a good example of those differences. In the original the siren don't end up with the prince and go live alone, but Disney to make their version did the 'and they all lived happily ever after' ending because Disney.
What you must have into consideration, though, is about the culture that you will take the tale from is open to this kind of things. There are some cultures that even when there is knowed a lot about them, they are still very protective of their own culture, and consider that every piece done without they consent is 'cultural apropiation'. In legal term that is still debated, because the knowledge is already there, and belong to the cultural heritage of all humanity, but is also true that a nation has a right to direct how their own culture is treated, and conserved. This is called knowdays as 'indigenous cultural heritage', and has been recogniced in some courts and treaties.
The line between cultural apropiation, and derivative work is blurry at best (at the final paragraph some ideas about this), but for now, if you have doubts, always remember to think this to yourself: 1) the tale can be traced to a defined folk people? If no, go ahead and do as you please. If yes, then 2) Is there a way to reach those folk people and ask for permission? If there is, go ahead. If there is no organization from them, go ahead.
And what if they don't give permission? You can respect them, or do something alike but with so much original material that can't be considered a derivative work, but just an original piece.
Of course if you belong to one of this ethnicities the tale belong to you, and you can create derivative work with it, because it belongs already to you and your ancestors.
To finish this lengthy legal advice, about the work itself, it will be an original derivated work, that means that it will have enough original material that it won't be confunded with the original piece (the folk tale), but it must credit the folk tale somewhere in the piece. A little phrase is often enough, such as 'based in the folk tale of La Llorona'.