In food processor, pulse tomatoes, cucumbers, bell pepper and shallot.
Add lemon grass, ginger, lime juice and zest, fish sauce, palm sugar, chile paste and herbs. Puree all ingredients together. Add coconut milk and combine. Taste and adjust accordingly, you may want more spice, a little saltier with more fish sauce, maybe a little sweeter with palm sugar, etc.
Pour into bowl and chill soup in refrigerator for several hours so flavors will meld together and soup gets very cold.
Serve topped with shrimp, additional chopped herbs or red pepper flakes, perhaps a swirl of more coconut milk, etc. Whatever you like!
