In a large bowl, combine rice flour, baking powder, salt and sugar. Mix to combine.
Add coconut milk and water and mix thoroughly until you have a smooth batter.
Fill a wok about 1/2 way with water. Place pandan leaves in the water. Place a metal rack in the water. On top of this, place a bamboo steamer.
Spray silicone muffin cups with non-stick spray. Place in the bamboo steamer. Fill muffin cups about 3/4 full with the puto batter.
Cover and turn heat on high and cook for 35 minutes. Remove the bottom steamer and cook for an additional 5 minutes.
Remove from steamer and leave to cool for 5 minutes. Puto will easily slide out of muffin cup.