Prepare an ice bath by placing ice into a large bowl filled with water.
Blend together the pandan leaves with the water. Strain the pulp from the pandan leaves and add the liquid to a sauce pan.
Add in the cornstarch, mung bean starch, wheat starch, sugar, pandan extract and lye water (if using). Turn on the heat to high, and stir the mixture with a spatula.
Once the mixture starts to thicken, reduce the heat to low and continue to cook until it becomes a translucent paste. Cook for another 2 more minutes.
Remove from heat and carefully transfer the paste to a potato ricer -- working in batches, squeeze the paste through the ricer over top of the ice bath, ensuring the "cendol noodles" are submerged in the ice water.
Leave the cendol in the ice water for 15 minutes.
Drain the cendol and set aside in the refrigerator until ready to assemble.
Make the sugar syrup:
In a small saucepan, combine the palm sugar and water and heat until thickened, about 5 minutes.
Transfer to a clean jar and let cool.
Assemble:
In a large, tall glass, layer cendol, azuki red beans, yellow mung beans, crushed ice, and drizzle with coconut milk and sugar syrup. Serve immediately.