Thailand, once

SIAM

This historic kingdom's name was officially changed in 1939, though it’s still used in the name of a famous Bangkok hotel chain.

This clue plays on Thailand’s historical name—Siam—which was officially used until 1939. The word "once" signals that you’re looking for a past name rather than the current one. It’s a straightforward history reference, so no tricky wordplay, just a nod to how countries rebrand over time.