Rather than redirecting {{Country data Siam}} to {{Country data Thailand}}, the former template transcludes the latter and passes through all parameters. The linked article will always be "Thailand", but the displayed name is either "Siam" or "Thailand" based on which of the two templates is used, even in templates that usually have a fixed default display name (such as {{flagcountry}} and {{fb}}). This allows for "Siam" to be used in historical contexts without having to also set |name=. The variants from {{Country data Thailand}} can be used with both templates.

Examples

Template Thailand output Siam output
{{flag|THA}}  Thailand  Siam
{{flag|THA}}  Thailand  Siam
{{flagcountry|THA}}  Thailand  Siam
{{flagicon|THA}} Thailand Thailand
{{bb|THA}}  Thailand  Siam
{{fb|THA}}  Thailand  Siam

Redirects to Template:Country data Thailand

Redirects to Template:Country data Siam