Spray a large nonstick wok or frying pan with cooking spray and heat over a high heat. Add the onion and stir-fry for 1–2 minutes until slightly softened. Add the garlic and chilli and stir-fry for about 1 minute until aromatic.
Add the carrot, baby corn, pak choi stems and tomatoes to the pan and stir-fry for about 3 minutes until softened. Transfer to a bowl.
Wipe the pan clean with kitchen paper, re-spray with cooking spray and heat over a high heat. Add the cooked rice and stir-fry for about 3–4 minutes until piping hot. Add the pak choi leaves, sweet chilli sauce and soy sauce with the reserved vegetables and toss together briefly until heated through. Remove from the heat and stir in the tofu and herbs. Ladle into warmed bowls and serve.