Thailand, once (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thailand once</span>' is the definition.<br/ ><span class="explanation-format__explanation">(former name of Thailand)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for siam that I've seen before include "An old country" , "Former name of Thailand" , "Thailand's former name" , "old-style country" , "The King and I nation" .)