Place the chicken thighs in the bottom of the slow cooker. Add the sweet potato cubes and diced onion on top.
In a small bowl, stir together the minced garlic, grated ginger, red curry paste, coconut milk, chicken broth, salt, and black pepper until smooth.
Pour the coconut milk mixture over the chicken and vegetables in the slow cooker. Stir gently to coat everything evenly.
Cover and cook on low for 6 hours or on high for 3 to 4 hours, until the chicken reaches an internal temperature of 165°F and the sweet potatoes are fork-tender.
Remove the chicken thighs, shred them with two forks, and return the meat to the slow cooker. Stir in the frozen peas and let the stew sit for 10 minutes on warm so the peas heat through.
Serve the stew over cooked rice and top each bowl with fresh cilantro.