Place the rice in a large bowl and add water to cover. Gently stir the rice with your hands, then drain the water, and repeat 4 or 5 times until the water runs almost clear. This removes the excess starch and prevents the rice from becoming gummy. Place the rinsed rice in a heatproof glass or stainless steel bowl that fits inside the inner pot of your Instant Pot. Add 1 cup of cold water to the bowl to cover the rice.
Pour 1½ cups water into the inner pot of the Instant Pot. Carefully lower the silicone trivet and bowl into the inner pot.
Secure the lid and set the Pressure Release to Sealing. Select the Pressure Cook setting at high pressure and set the cook time to 13 minutes.
Once the timer has completed and beeps, allow a natural pressure release for about 10 minutes and then switch the Pressure Release knob from Sealing to Venting to release any remaining steam.
In a small saucepan, bring 2/3 cup of the coconut milk to a simmer over medium heat. Add 5 tbsp of the cane sugar and 1/4 tsp of the salt and whisk until the sugar is dissolved and the milk tastes salty-sweet. Keep the sauce warm.
Transfer the cooked rice to a large bowl and pour the coconut milk mixture on top. Stir well to combine and gently fluff with a fork. Cover and let it sit until the liquid is absorbed (about 25 minutes).
Meanwhile, set aside 2 tbsp of the remaining coconut milk in a small bowl. Wipe out the saucepan and add the remaining coconut milk. Add the cornstarch to the small bowl and whisk until smooth, forming a slurry. Bring the coconut milk in the saucepan to a simmer over medium heat, whisking frequently. Whisk the slurry into the coconut milk on the stove and simmer until the mixture has thickened, about 2 minutes. Whisk in the remaining 2 tbsp cane sugar and the remaining 1/4 tsp salt until the sugar is dissolved. The coconut cream should be slightly saltier and less sweet than the coconut milk mixture used to cover the rice.
When ready to serve, use a 1-cup measuring cup to scoop the coconut rice into mounds on individual plates and arrange the sliced or diced mango alongside. Drizzle the warm coconut cream over the rice and garnish with the toasted yellow mung beans or sesame seeds. Serve immediately. Do not warm up or refrigerate, as the rice will turn rock hard.