Heat milk, sugar and salt in large saucepan over medium heat, stirring occasionally, 5 min. or until bubbles start to form at edges. Meanwhile, whisk egg yolks until smooth in large heat-proof bowl. Gradually whisk half the hot milk mixture into the bowl of yolks. Pour into saucepan mixture and whisk over medium-low heat. Cook, stirring constantly without boiling, 8 to 10 min., or until custard coats back of spoon.
Remove from heat. Whisk in coconut milk, vanilla, cinnamon, allspice and nutmeg. Strain into punch bowl or pitcher. Cover and refrigerate 3 hr. or until cold (can be made up to this point one day in advance and kept covered and chilled). Whisk in rum and sprinkle with coconut to serve.