Hallo. I see you are wondering what to put in your soap as I am doing at the moment Unfortunately MY opinion is that you won't get any benefit of them putting them in a soap two reasons:
1. Tranexamic acid and Kojic acid are acids and they will turn into SODIUM salts which I doubt are effective. Otherwise they would be sold as sodium salts as well.
2. Tranexamic acid is used to prevent excessive bleeding as injection. Kojic acid is used as chemical peeling in the form of creams or solutions. It has to spend some time on the skin to exfoliate (more than 30-40 seconds - time that soap spends on skin).
I advice you to give up with this two. You may achieve some effect but you can't be sure what, even if you make new type of soap.