Peel the cucumbers, cut them lengthwise in half, and remove the seeds with a spoon if they are large. Slice the cucumbers into thickish half-moons and put them in a large bowl. Season with salt and pepper, sprinkle lightly with fish sauce, then add the ginger and a couple of tablespoons of palm sugar. Toss well, and let the cucumbers sit for 5 minutes or so.
Add a good spoonful of finely chopped serrano or jalapeño chiles (seeds removed, if desired, to lessen spiciness) or finely slivered Thai chiles. Squeeze over the juice of 2 limes and toss again, then cover and refrigerate till serving.
Just before serving add a fistful of roughly chopped mint and basil leaves. Taste and adjust the seasoning with lime juice as well as salt and pepper. Garnish with thinly sliced scallions or paper-thin slices of sweet onion.