In a large pot, bring the water or chicken broth to a boil.
Add the lemongrass, galangal, and kaffir lime leaves. Reduce the heat and simmer for about 10 minutes to infuse the flavors.
Add the sliced mushrooms and tomatoes to the pot.
Cook for about 5 minutes until the mushrooms are tender.
Add the shrimp and cook for another 2-3 minutes until they turn pink and are cooked through.
Stir in the fish sauce, lime juice, Thai chili paste, and sugar.
Adjust the seasoning to taste, adding more fish sauce, lime juice, or sugar if needed.
Ladle the Tom Yum Goong into serving bowls.
Garnish with fresh cilantro and serve with lime wedges on the side.
Enjoy your meal!