In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the diced chicken thighs and season with salt and pepper. Cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.

In the same skillet, add the diced onion and minced garlic. Sauté for 2-3 minutes until the onion is translucent.

Add the mixed vegetables to the skillet and cook for another 3-4 minutes until heated through.

Push the vegetables to one side of the skillet and pour the beaten eggs into the empty side. Scramble the eggs until fully cooked, then mix them with the vegetables.

Add the cooked rice to the skillet along with the cooked chicken, soy sauce, teriyaki sauce, and sesame oil. Stir everything together and cook for an additional 3-4 minutes, allowing the rice to heat through and absorb the flavors.

Remove from heat and stir in the sliced green onions. Adjust seasoning with additional salt and pepper if needed.

Serve hot, garnished with sesame seeds if desired.