Heat ½ tsp olive oil in a large skillet over medium heat.
Add chopped chicken thighs; cook until browned and cooked through. Remove and set aside.
In the same skillet, heat remaining olive oil. Add onion, green bell pepper, celery, and carrots. Stir-fry until slightly tender.
Pour in boiling water, soy sauce, chicken bouillon cube, salt, and sugar. Stir well.
Add bok choy and bean sprouts. Cook for 2–3 minutes until veggies are just wilted.
Return chicken to the skillet and mix everything together.
Stir water and cornstarch in a small bowl, then pour into the skillet to thicken the sauce.
Cook for another 1–2 minutes until everything is coated in a glossy sauce. Serve hot.