In a small bowl, whisk together the soy sauce, 2 tablespoons water, honey, rice vinegar, minced garlic, and minced ginger until combined to make the teriyaki sauce.
Heat 1 tablespoon vegetable oil in a large skillet over medium-high heat.
Add the bite-sized chicken thigh pieces to the hot skillet and cook, stirring occasionally, until browned and cooked through, about 8–10 minutes.
Pour the prepared teriyaki sauce over the cooked chicken and bring the mixture to a simmer.
In a separate small bowl, stir 1 tablespoon cornstarch into 2 tablespoons cold water to make a slurry, then pour it into the skillet and stir until the sauce thickens, about 1–2 minutes.
Remove from heat and garnish with sliced green onions and sesame seeds before serving.