Place the chicken thighs in the slow cooker.
Whisk the honey, soy sauce, tomato paste, rice vinegar, sesame oil, garlic, and ginger together, then pour over the chicken.
Cover and cook on low for 4 hours, until the chicken is tender and reaches 165°F.
Transfer the chicken to a board and cut or shred it into bite-size pieces.
Whisk the cornstarch with water, stir it into the sauce, cover, and cook on high for 10 minutes until glossy and thickened.
Return the chicken to the sauce, toss to coat, and garnish with sesame seeds and green onions.