In a small bowl, whisk together the sauce ingredients until the sugar has dissolved. Set aside.
Heat the oil in a wok or heavy skillet over medium-high heat. Once the oil is shimmering, add the sliced shallot, garlic, and Thai chilies. Cook for 1-2 minutes, stirring often to keep the garlic from burning.
Add the diced chicken to the wok and cook for 2-3 minutes, stirring occasionally, until the chicken is starting to brown. Add the mushrooms and the light green/white parts of the green onion to the wok. Cook for 3-4 minutes, until the mushrooms are starting to get soft.
Add the remaining veggies and the sauce and cook, stirring often, until the green beans are no longer raw and the sauce is starting to reduce. Stir in the Thai basil leaves and the dark green scallion pieces. Cook 2-3 minutes until the Thai basil is wilted and fragrant. Season to taste with salt if needed and serve over steamed jasmine rice.
