Remember chillies are hot so you can remove the seeds (I don't) and start maybe with one chilli and taste. It is most important to taste. Once added you cannot take away so if this is your first time with Thai food add 1 chilli, 1 tablespoon fish sauce, half of the lime juice and taste! Then if required add more and taste. I love fish sauce, chillies and lime but taste and add more if required.