Most people don't know that red curry paste is not vegetarian friendly. Shrimp paste is one of key ingredients in red curry paste. To have a real vegetarian curry, you must start with vegetarian curry paste. Unless you can find a home-made vegetarian curry paste, it's not available in stores. Even in Thailand, outside of vegetarian food festival, you will have to hunt for vegetarian curry paste.
I made this recipe for my friend and her family. They love Thai food and Thai curries.