Thinly slice the cucumbers and red onion, then place them in a colander. Sprinkle with salt and toss to coat. Let sit for 10 minutes to draw out excess moisture.

In a small bowl, whisk together the lime juice, fish sauce, sugar, and minced garlic until the sugar dissolves.

Rinse the salted cucumbers and onion under cold water to remove excess salt, then pat dry with a clean towel or paper towels.

In a large mixing bowl, combine the cucumbers, onion, lime dressing, cilantro, mint, and peanuts. Toss gently to coat everything evenly.

Let the salad rest for 10 minutes to allow the flavors to meld. Taste and adjust seasoning if needed—add more lime for acidity or sugar for sweetness.

Transfer to a serving bowl, garnish with extra herbs and peanuts if desired, and serve immediately.