This is one of my favourite Thai desserts. It is called Khanom Tuay (ขนมถ้วย). I bought it at Wat Takien Floating Market. However, you can buy it from almost everywhere. Ingredients are basically rice flour, coconut milk and sugar. The recipe does vary a bit. I prefer the one with the second green level which comes from the juice of the pandanus leaf. The lady here told me that she steams them for only 5 minutes.