1. Soak purple tuatua with salt water for 30 mins then scrub it. Shred kaffir lime leaves. Dice lemongrass root.
2. Slice galangal. Cut straw mushroom into two pieces. Cut cherry tomato into two pieces. Squeeze lime juice.
3. Put lemongrass, galangal, straw mushroom, hot pepper into boiling water, cover the lid and cook for 10 mins.
4. Put in fish sauce, Nam Prik Pow Thai chili paste, cook for 1 min, put in kaffir lime leaves, coconut milk, cherry tomato and mix well, cover the lid and cook until boiled.
5. Put in purple tuatua, cover the lid and cook for 4 mins. Finally, off the heat and put in lime juice.