Firaxis has today given us one of the last civ guides for the base game, and we got a surprise reveal, which nobody had on their radar: Siam. This surprise also ensures that we cannot have both Britain and Germany in the base game, which will certainly spark interesting discussions. For an overview over all civs please see this thread.
Siam is a cultural and diplomatic civ with a starting bias for ivory. Siam gets a lot of boni related to city states and friendly relationships with them, including from their associated wonder, the Doi Suthep. For more info about Siam please check this thread.