Rice noodles, aka rice sticks, come in different widths; for this dish, get the ones that are about 2mm (less than ⅛in) wide, which are sometimes labelled pad thai noodles.
Simmer until the prawns are cooked through. Finally, add the drained noodles and stir well – I find a couple of pasta forks, one in each hand, best for this – so that everything is combined ...
Just before serving, cook the noodles in a pan of boiling water according to the packet instructions. Drain and divide the noodles between six soup bowls. Ladle the hot soup over the top to serve.