Heat the coconut oil in a large deep pan and cook the chicken thighs over a medium heat until golden brown, about 5 minutes on each side.
While the chicken is cooking prepare all of the other ingredients and put a pot of water on to boil for the noodles.
Remove the chicken and set aside. Add the curry paste to the same pan and fry for 3 minutes. While the paste is cooking slice the chicken into thin strips.
Add the chicken broth, coconut milk, lime leaves, fish sauce, lime juice and chicken strips to the pan. Bring to a simmer and cook for 10 minutes, until chicken is cooked through. Add the spinach leaves for the last 2 minutes and taste the soup for salt.
While the soup is cooking boil the noodles as per the packet instructions and drain.
To serve, put some noodles into the bottom of each bowl, ladle over the soup and top with sprouts, coriander, mint and some optional sliced red chilli.