Over at my Thai Life Blog, I'm showing the set of Thai condiments you traditionally find on a table in Thailand. Just as you have salt and pepper, we have our set of condiments too.
They are: dried flaked chillies for spice (or sometimes a dark strong chillie sauce), vinegar for sour, sugar for sweet and fried garlic for, warding off vampires. You can add fish sauce to that if you like, for saltiness and when serving noodles I usually swap the sugar for crushed peanuts. Crushed peanuts are expensive so you won't see them given away so freely in street stalls, but they're popular.