To make bottom layer: Put agar-agar powder and water in a pot and bring to a low boil. Add strained syrup, salt and thick coconut milk. Bring to a boil, then add the milk and turn off the heat immediately. Pour into a wet mould. Leave aside to partially set.
To make top layer: Combine sugar, water and agar-agar powder and bring to a boil. Add coconut milk and sweetcorn, and stir well. Lastly, add milk. Pour mixture over half-set bottom layer. Leave aside to cool, then chill well before serving.