We had this on our anniversary/retirement trip to Thailand and found this recipe to recreate it upon our return to the cold.
Thoroughly rinse the rice until the water stays clear, then soak the rice overnight.
Drain the rice and spread evenly in a steamer lined with cheesecloth. Cover and steam until the rice is tender (between 20 mins and 1 hour!).
Reserve 3 tbs of the top of the coconut milk. Bring the remaining coconut milk to the simmer and dissolve the sugar and salt in it, stirring constantly. Pour into a bowl to cool. When cooled add the rice, stir well and leave to stand for 10-15 mins.
Spoon the rice onto individual serving plates. Arrange the mango slices on one side and drizzle with the reserved coconut milk. Decorate with the lime rind and serve.