Put the birdseye chillies, ginger, blachan, garlic, shallots and sugar into a food processor and blend to a coarse paste, adding a little of the tamarind water if needed.
Bring the chicken stock and the rest of the tamarind water to the boil in a pan. Add the spice paste and simmer for 10 minutes. Strain through a fine sieve. Add the fish sauce and the beans and simmer for one minute.
Add the monkfish and squid and simmer for one minute, then add the bok choi and simmer for a further minute.
Ladle into warmed bowls and serve sprinkled with the coriander leaves and red chilli.