Rinse the tuna with diluted salt water and drain. Heat the cooking oil in a pan over medium heat, then fry the tuna until golden on both sides. Remove and set aside on a plate.

In a pot, add 2 tablespoons of the oil used for frying the tuna and the sugar. Cook until the sugar turns a caramel color, then add the minced shallot and garlic. Sauté until fragrant, then pour in the coconut water. Add the seasoning powder and fish sauce. Bring to a boil before adding the fried tuna.

Add the whole chilies to the pot. Cook over high heat until boiling, then reduce to medium heat and simmer the tuna for 30 minutes. Adjust the seasoning to taste, then turn off the heat.