Even though most people living in Bangkok buy store bought curry pastes, nothing compares to the scent of the curry paste being made. It perfumes the whole kitchen. The arduous process, from sourcing the ingredients to pounding out the paste, is daunting but the reward is grand.
Often store bought green curry paste is too spicy so that I can't put enough paste in without having the curry be too hot. When you make it yourself, you will be able to control the heat in your own curry paste by adjusting the amount of green chili peppers you add.
Green curry paste's ingredients are the same as red curry paste, except for the chilies. The red in red curry paste comes from dried chili peppers, while the green in green curry paste comes from fresh green chili peppers. Green chilies turn from red when ripe.
Don't worry about making too much: you can store excess in your freezer for up to a year.