Rinse, peel and halve the cucumber. Cut into slices and place in a bowl. Peel the mango and cut into cubes. Rinse the chiles, remove the seeds and chop.
Rinse the cilantro, pat dry with paper towels and chop the leaves small. Mix the diced mango, the chiles, the peanuts and the cilantro with the cucumber slices, vinegar and peanut oil. Season with salt and sugar.