Toss chicken first in 1 tablespoon of the soy sauce, then in the flour, coating pieces evenly. Heat the oil in a large frypan over medium high heat. Place chicken in the frypan, cook and stir chicken until browned, about 5 minutes. Remove chicken.
Reduce heat to medium and stir in curry paste. Cook for 1 minute until fragrant, then stir in green onions, garlic and ginger; cook an additional 2 minutes. Return chicken to the pan, stirring to coat with the curry mixture. Stir the coconut milk, fish sauce, the remaining soy sauce and sugar into the chicken-curry mixture. Allow to simmer over medium heat for 20 minutes until the chicken is tender. Serve garnished with coriander leaves.