Cut the cucumber into thin strips and slice the tomato after removing the stem.

Rub the chicken thigh with sugar and salt using your hands.

Wrap the chicken tightly with plastic wrap twice and place it in a heat-resistant storage bag, sealing it to remove air.

Boil water in a pot, add the bagged chicken, cover, and cook on low heat for 15 minutes. Flip once during cooking, then turn off the heat and let it sit for 10 minutes.