The crossword solution for the term 'Neighbor of Siam' is Laos, which is a 4-letter word. Laos is a landlocked country located in Southeast Asia, bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the south, and Thailand to the west. It is also known as the Lao People's Democratic Republic and is one of the few remaining socialist states in the world. Laos is the neighbor of Siam, now known as Thailand.