Ask the average person what laksa is and they'll probably describe a dish of noodles in a rich curry-flavoured coconut milk broth with seafood. But there are many other types of laksa and, within Malaysia and Singapore, there are regional variations of each one.
The curry laksa (also called laksa lemak) is probably the most common type and plenty of places serve good versions of it in Hong Kong. The broth should be rich, but not too rich - it's a soup, not a sauce. If I get a craving for this dish at home, I head straight to my kitchen, where I keep a supply of Prima Taste packaged curry laksa, which is one of my favourite varieties of instant noodle (actually, they're not quite "instant": the noodles take seven minutes to cook).
From scratch, making curry laksa is a lot of work and it's not worth doing for a small batch - it entails making a laksa paste from belacan (dried shrimp paste), shallots, turmeric, chillies and lemongrass; a seafood broth with coconut milk; and a sambal. Then you need noodles, bean sprouts, shrimp, bean curd puffs, fish cakes, curry leaves and hard-boiled eggs to complete the dish.
Assam laksa is much harder to find in Hong Kong; so far, my favourite version is the one served at Café Malacca, at the Traders Hotel (last week rebranded as Hotel Jen), in Western. The rice noodles are served in a broth with complex flavours: it's tart (from the assam, aka tamarind), fishy, spicy and pungent from the otak udang (a thick, dark shrimp paste), with bright notes provided by fresh pineapple, mint leaves and cucumber. Assam laksa is also called Penang laksa because it's a speciality of that region of Malaysia.
You'd probably have to travel the length and breadth of Malaysia and Singapore to taste all of the many regional versions of laksa, but the one thing they have in common is that they contain noodles. And even those can vary wildly.