Heat the vegetable oil in a medium pot over medium heat. Add the red curry paste and fry for about 2 minutes until fragrant.
Pour in the boiling water and coconut milk, stirring until smooth and combined. Season the broth with soy sauce, fish sauce, and sugar. Taste and adjust to balance the salt, sweetness, and spice.
Add the pak choi (or spinach) and drop in the frozen dumplings straight from the packet. Simmer gently for 5 minutes, or until the dumplings are cooked through.
Serve hot, topped with chilli oil, fresh herbs, spring onions, and a squeeze of lime.