Thai recipes are not supposed to be vegetarian. They like their seafood and their meat, and create magic with it.
Also check out vegetarian pad thai recipe.
Vegetarian Thai Tom Kha Soup
1. Discard the bottom 2 inches of the lemongrass. Discard the top woody part and use the middle portion (about 8″ of it) for the soup. Cut this part into small circles and set aside.
2. Roughly chop the galangal, chillies, and shallots. Tear the limes leaves into two.
3. Bring water or vegetable stock to a boil and lower fire to a simmer. Add the galangal, lemongrass, shallots, chillies, sugar, and lime leaves. Keep on simmer for 5-7 minutes.
4. Add the coconut milk and the tofu and mushrooms with some salt. Keep on simmer for another 7-10 minutes until the mushrooms are soft.
5. Remove from fire. Squeeze in fresh lime starting with half a lime and then increasing the quantity as you like. Garnish with roughly torn coriander leaves / cilantro. Serve hot.