Place the chia seeds and coconut milk in a clean, sealable container or bowl. Add the honey and vanilla extract immediately. Stir everything together thoroughly with a spoon or whisk, ensuring the chia seeds don't clump on the bottom. Let the mixture rest for five minutes, then stir vigorously once more for even distribution.
Seal the container or cover the bowl well. Place the mixture in the refrigerator to set. Let the pudding rest undisturbed for at least four hours, but preferably overnight. This allows the chia seeds to absorb the liquid and develop the thick, desired texture.
Shortly before serving, peel the half mango and cut the flesh into small, even cubes. Remove the set chia pudding from the refrigerator and give it a quick stir with a spoon.
Divide the chia pudding among your desired bowls or glasses. Top with the mango cubes. Finally, scatter the pumpkin seeds over the top and serve immediately.