Place the chicken thighs in a steamer set over boiling water for 10–12 minutes until cooked through. Alternatively, simmer them in shallow water in a frying pan for 10 minutes. Remove from the steamer or pan and set aside to cool.
Meanwhile, cook the rice according to the packet instructions. Drain and rinse under cold water to cool the rice completely, then tip it into a large bowl.
Make the dressing: mix together the lemon juice and peanut butter, if using, until well combined, then whisk in the oil.
Dice the chicken thighs into bite-sized pieces and stir into the rice. Add the pineapple, red pepper, sugar snap peas and peanuts, if using. Pour the dressing over the chicken rice salad and serve.