Heat coconut oil in a medium pot over medium heat.
Add Tom Yum paste and cook for about 30 seconds, until fragrant.
Add the rice and stir for about 1 minute so it absorbs the spices.
Pour in the water and simmer for about 10 minutes, until the rice begins to soften.
Add mushrooms and tomatoes and cook for another 3–4 minutes.
Slice the squid into small pieces and add it together with the shrimp.
Cook for 2–3 minutes, just until the seafood is tender.
Stir in the coconut milk and gently heat the soup.
Taste and add lemon or lime juice if desired.
Serve topped with freshly chopped cilantro.