Preheat a large ridged grill pan on medium heat until hot.

In a large bowl, combine chicken thighs with vegetable oil and 1 teaspoon of fish sauce, ensuring even coating.

Grill the chicken in batches for 7-9 minutes, flipping once, until cooked through and juices run clear when pierced.

Remove the chicken from the grill and place on a plate to cool slightly.

Cut the cooled chicken into 1/2-inch chunks.

In a separate large bowl, whisk together lime juice, garlic, brown sugar, chili sauce (Sriracha), and the remaining fish sauce until well combined for the dressing.

Thinly slice the green cabbage and add it to the bowl with the dressing.

Toss the cabbage to coat it evenly with the dressing.

Let the cabbage mixture stand while preparing the remaining ingredients.

Thinly slice the red onion and coarsely chop the romaine lettuce, cilantro, and mint.

Add the sliced onion and chopped greens to the bowl with the cabbage.

Chop the roasted peanuts and add them to the bowl, along with the grilled chicken and any accumulated juices.

Toss all ingredients together thoroughly to combine.

Garnish the salad with additional cilantro and mint before serving.