Do take your time and pick at your food; enjoy the conversation and the laughter and the sense of community.
Do pick up the check if it comes to you; in Thai society the person who is perceived to be the richest pays. Nine times out of ten this will be you. On the other hand don't try to contribute if someone else is paying the bill, it takes away from their status and 'face'.
Do make sure to take only small portions of each dish so there's enough to go around.
Do finish everything on your plate; it lets the host know you enjoyed the meal.
Do let the senior ladies of the group do the ordering; it's tradition.
Do wait for the host to invite you to dig in.
Do expect a wide variety of dishes and flavours; part of the trick to ordering Thai food is to get a balance of sweet, sour, salty and spicy.
Do serve yourself but only what you can eat in two or three mouthfuls.