Place the chicken thighs in the bottom of a 6-quart slow cooker.
In a medium bowl, whisk together the chicken broth, soy sauce, honey, rice vinegar, tomato paste, garlic, and ginger until well combined. Pour the mixture over the chicken.
Cover the slow cooker and cook on low for 6 hours or on high for 3 hours, until the chicken is tender and easily shreds with a fork.
In a small bowl, mix the cornstarch and cold water until smooth to create a slurry. Stir the slurry into the slow cooker sauce to thicken it.
Increase the slow cooker to high and cook uncovered for an additional 15–20 minutes, or until the sauce has thickened to desired consistency.
Shred the chicken in the slow cooker using two forks, mixing it into the sauce.
Serve the chicken over steamed rice, garnished with sliced green onions and sesame seeds.