Combine lemon juice, sugar, salt, white pepper, fish sauce, and chili pepper in a large bowl.

Stir until sugar dissolves completely.

Quarter the tomatoes.

Use a spoon to remove and discard the pulp and seeds from the tomatoes.

Slice the tomato wedges into fine slivers.

Add the sliced tomatoes to the bowl with the lemon juice mixture.

Add the shredded chicken, shredded cabbage, chopped mint, and chopped cilantro to the bowl.

Toss all ingredients together until well combined.

Adjust seasoning to taste with additional salt, white pepper, or chili pepper.

Refrigerate the salad for 1 hour to allow flavors to meld.

Serve the salad chilled, garnished with additional sprigs of mint and cilantro.