4 whole-wheat hamburger buns, toasted
1 tbsp. extra-virgin olive oil
1½ cups coleslaw mix
1 tbsp. rice vinegar
2 tbsp. sweet chili sauce, such as Mae Ploy
¾ cup precooked brown rice, such as Uncle Ben's
⅓ cup shredded red beet
½ tsp. salt
½ tsp. chili powder
1 tsp. ground pepper
2 tsp. low-sodium soy sauce, divided
⅓ cup walnuts
1 (15 ounce) can no-salt-added kidney beans, rinsed