Adjust oven racks to upper-middle and lower-middle positions and heat to 400 degrees. Spray 2 rimmed baking sheets with vegetable oil spray. Toss 2 pounds ground beef, 2 teaspoons salt, 2 teaspoons water, and ½ teaspoon baking soda together in bowl until thoroughly combined. Let sit for 20 minutes.

Combine ¾ cup potato flakes, 1 egg, 1 tablespoon vinegar, and remaining ¾ cup water in small bowl, stirring until smooth. Add mixture to meat along with 2 chopped shallots, ¼ cup cilantro, 2 tablespoons mint, 4 garlic cloves, 2 Thai chiles, 2 teaspoons ginger, and 1 teaspoon pepper. Mix with hands until well combined. Working with 2 tablespoons at a time, shape into 2-inch patties (about 32 total). Arrange on sheets.

Roast until bottoms are golden brown, about 15 minutes, switching and rotating sheets halfway. Transfer sheets to wire racks and set aside.

Heat 2 tablespoons oil in Dutch oven over medium heat until shimmering. Add 2 chopped shallots and ¼ teaspoon salt; cook until softened, 4 minutes. Stir in 15–20 curry leaves, 2 Thai chiles, 2 garlic cloves, 1 teaspoon garam masala, and ½ teaspoon turmeric; cook until fragrant, 1 minute. Stir in tomatoes, coconut milk, and 2 tablespoons vinegar. Gently stir in cooked patties; bring to boil. Reduce heat to medium-low and simmer for 5 minutes. Season with salt. Sprinkle with 2 tablespoons cilantro and serve.