In a small mixing bowl, combine the soy sauces, oyster sauce, brown sugar, fish sauce, and hot water. Stir well until the sugar has fully dissolved, then set aside.
Place a wok or a heavy-bottomed skillet over medium-high heat and add the neutral oil. Once the oil begins to shimmer, sauté the shallot, garlic, and chopped chilies for 1 to 2 minutes, ensuring the garlic doesn't brown.
Introduce the chopped chicken to the pan, cooking for 2 to 3 minutes until it begins to sear and color lightly. Add the mushrooms and the pale parts of the scallions; continue to cook for another 3 to 4 minutes until the mushrooms begin to soften.
Incorporate the red bell pepper and green beans, then pour in the prepared sauce. Stir frequently as the vegetables cook and the sauce reduces slightly, about 4 to 5 minutes.
Add the Thai basil leaves and the reserved dark green scallion tops. Stir everything together and cook for another 2 to 3 minutes until the basil is wilted and fragrant. Taste and adjust seasoning with salt if desired. Serve immediately over steamed jasmine rice.