In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.
Add the minced garlic and finely chopped bird's eye chilies to the hot oil. Sauté for about 30 seconds, stirring constantly until fragrant but be cautious not to let the garlic burn.
Incorporate the sliced chicken thighs into the skillet, stirring frequently. Cook for approximately 5-7 minutes until the chicken is browned and no longer pink inside.
Toss in the sliced red bell pepper and continue to sauté for an additional 2-3 minutes, or until the peppers have softened slightly.
In a small bowl, whisk together the soy sauce, oyster sauce (if using), fish sauce, and sugar until the sugar is dissolved.
Pour the sauce mixture into the skillet with the chicken and peppers, stirring well to ensure everything is coated evenly. Allow it to cook for another minute, letting the flavors meld together.
Remove the skillet from heat and gently fold in the fresh Thai basil leaves, stirring just until they are wilted but retain their vibrant color.
Spoon the spicy Thai basil chicken onto plates over a generous serving of jasmine rice.
Notes
To elevate your dish, garnish with a few whole basil leaves on top and include a slice of lime on the side.