The clam which is most readily available in the market is the undulated surf clam , Paphia undulate , called  hoi lai , The shell is covered with a pleasing pattern of branching lines and grows 5-6 cm long..  The cockle , Anadara granosa and A. nodifera , called hoi khraeng, in Thai , and also known in English as the ark shell and as the blood cockle , has a thick , highly arched shell with ridges radiating from the hinge . The shell , 5-6 cm long , is white near the hinge and brown near the  opposite margin.  The mussel , Perna viridis , called hoi  malaeng pu , in Thai , has a dark brown shell which is green at the margin and reaches a length of 20 cm.               

Cleaning               

                     Purchase live cockles , mussels , and clams , which can be seen to open and close their shells . They are washed free of the mud and sand which may accompany them and cleaned with a brush . The fibers by which mussels anchor themselves are trimmed. Next , they are soaked in clean water for a time to allow them to cast out any dirt they contain . After a final washing , they are usually either broiled or covered with boiling water . When the shells open , they are done. 

Oysters  and Scallops               

                     The oyster , Crassostrea gigas , Called hoi nang rom ,in Thai, has a rough shell 9-20 cm long . Oysters are bought live and the shells should be closed . They are washed and scrubbed clean with a brush , and then opened using a sturdy knife with a short , thin blade. The more cup-like of the two shells is held downward either on a piece of thin cloth in the hand  or on a firm support. The blade of the knife is carefully worked in between the shells , the muscle holding the shells together is cut , and the knife is moved around the margin to free the oyster from the upper , flat shell , which is removed . The blade is then run under the oyster to free it from the lower shell in which it is now contained , and any shell fragments on it are picked out.      The Scallop , Amusium pleuronectes , called hoi chen , in Thai ,  and also hoi phat , in Thai , has a fan – shapped shell 7 – 15 cm long, which looks lik the trademark of the oil company Shell , pronounced chen in Thai . The part of the scallop that is the chief interest here is the muscle that holds the shells together . After opening a scallop , free the muscle from the shell and wash it clean.