To make the chicken marinade, combine 1/4 cup of low-sodium soy sauce, 1 garlic clove minced, and 1 tbsp of brown sugar in a bowl. Marinate the chicken in the mixture for at least 20 minutes, making sure that it is well submerged and all of its surfaces are covered by the marinade.
To make the noodle sauce, combine 3 1/2 tbsp of smooth peanut butter, 3 tbsp of soy sauce, 1 tbsp of fish sauce, 2 tbsp brown sugar, 1/4 cup of warm water, and 1/2 tsp of salt in a mixing bowl using a whisk until smooth. Set aside. Grind 2 cloves of garlic, 1 red chilli, 1/4 tbsp brown sugar, and 1 tbsp canola oil together using a mortar and pestle or a food processor until they become a paste. Set aside.
Cook the flat rice noodles according to packaging's instructions. Drain off excess water and set aside.
In a wok or a frying pan, heat about 1 tbsp of canola oil over medium high heat. Add in 1 clove of garlic minced and stir fry until fragrant and tender. Add in the baby bok choys and stir fry until cooked, about 3-5 minutes. Remove the bok choys from the pan and set aside.
To make the chicken, add about 1/2 tbsp of canola oil onto a pan and cook the marinated chicken over medium high heat on a frying pan for about 4-5 minutes on each side or until cooked thoroughly. Make sure the pan is not too hot and be careful not to burn the exterior. Remove from heat and let cool. Once the chicken is cooled, cut into smaller, bite-sized pieces.
Add another 1 tablespoon of canola oil to a wok or a pan and heat over medium high heat. Add the garlic-chilli paste and stir fry until fragrant, about 20 seconds. Stir in the peanut butter noodle sauce mixture and stir for about 2 minutes. Add in the cooked rice noodles, chicken, and baby bok choys and mix well until all the noodles are covered with the sauce. If the sauce is too thick, add about 1 tbsp of warm water.
Once the noodle is well covered with the sauce, turn off the heat and add in 1 1/2 to 2 tbsp of lime juice, chopped coriander, and chopped green onions and mix well.