What's the best practice for storing an OAuth token in WinForms?

I was wondering what is the best fit for storing the authentication token.

My use case would be that the user can enable "Remember Authentication" and will need to re-authenticate when the token expires. Otherwise, it will be just for "session".

I was going to use a singleton class for this and update the custom parameter if the Remember Authentication option is enabled, but I was wondering if this is not secure or if there is a better way to do it.