Thai soup infuses bold aromatics into light broth in minutes — not hours of simmering. Aromatics are bruised to break cell walls and release essential oils, simmered briefly, left in the bowl or strained. Finishing flavours (fish sauce, lime juice, chilli paste) go in off heat to preserve brightness.
Aromatics are bruised not chopped fine — lemongrass smashed and cut 2-inch, galangal sliced thick, kaffir lime leaves torn. They're structural, not eaten. Simmer 5–8 minutes to infuse. Protein goes in near the end. Critical finishing off heat: fish sauce, lime juice, nam prik pao. Lime juice must go in last and off the boil — cooked lime juice loses brightness. Balance should hit sour, salty, spicy, sweet, and herbal.
For tom kha, thin coconut milk replaces stock — still not boiled hard. The difference between good and great tom yum is the lime — squeeze in at the last second, after ladling into bowls. Fresh bird's eye chillies crushed in the bowl give sharp heat; chilli jam gives smoky lingering heat. Use both. Street-level quality means thin clear broth, intensely aromatic, aggressively sour-spicy.
Chopping aromatics fine as if they'll be eaten. Boiling vigorously with aromatics. Adding lime juice while on heat. Not bruising lemongrass and galangal enough. Using dried aromatics. Treating nam prik pao as optional — it's the smoky backbone. Over-cooking prawns.