Prepare the chili fish sauce by mixing the chopped red chili pepper, 3 tablespoons of fish sauce, and juice from one lime wedge in a small bowl. Set aside.
Heat the cooking oil in a wok or large skillet over high heat.
Add the minced garlic and sauté briefly until fragrant, then push to the side of the wok.
Pour the beaten eggs into the center and scramble until mostly set.
Add the cooked jasmine rice to the wok. Stir-fry vigorously, breaking up any clumps and mixing well with the eggs and garlic.
Season the rice with 1 tablespoon soy sauce, 1 tablespoon fish sauce, and a pinch of sugar. Toss to coat the rice evenly.
Gently fold in the lump crab meat and chopped scallions. Cook for another minute, being careful not to break up the crab chunks, until everything is heated through.
Remove from heat immediately.
Serve hot, garnished with cucumber slices, cilantro, and a lime wedge, with the chili fish sauce on the side.