Tom Yum Nam Sai — Thai clear prawn soup
A fragrant, clear Thai soup with prawns, galangal, lemongrass and lime — light, punchy and ready in under 40 minutes.
Light, aromatic and sharply flavoured, Tom Yum Nam Sai is the clear-broth cousin of the richer tom yum. It’s all about bright, clean flavours — galangal, lemongrass and kaffir lime go toe-to-toe with fish sauce and lime juice.
Make this when you want something restorative but exciting: perfect as a starter for a Thai feast or a quick midweek supper that still feels special.
Ingredients
- 1.2 l chicken stock — use low-salt if preferred
- 400 g raw king prawns — peeled and deveined
- 30 g galangal — fresh, sliced into 3–4 mm rounds
- 2 lemongrass — outer leaves removed, stalks bruised and halved lengthways
- 4 kaffir lime leaves — torn to release oils
- 2 shallots — thinly sliced (about 60 g)
- 15 g palm sugar — or soft light brown sugar
- 150 g chestnut mushrooms — sliced
- 200 g cherry tomatoes — halved
- 3 bird's-eye chillies — smashed — adjust to heat preference
- 45 ml fish sauce
- 45 ml lime juice — about 2–3 limes
- salt — to taste
- 20 g fresh coriander — roughly chopped, for garnish
- 2 spring onions — sliced on the diagonal, for garnish
Equipment
- large saucepan
- ladle
- fine sieve
Instructions
Prepare the aromatics: bruise the lemongrass halves with the back of a knife, slice the galangal, tear the kaffir lime leaves and smash the bird's-eye chillies. Thinly slice the shallots and halve the cherry tomatoes.
Pour the chicken stock into a large saucepan and add the prepared galangal, lemongrass, kaffir lime leaves, smashed chillies and shallots. Bring to a gentle simmer over medium heat and let it infuse for 10 minutes.
Add the sliced chestnut mushrooms and halved cherry tomatoes to the simmering stock and cook for 3 minutes so they soften but keep texture.
Reduce the heat so the broth is barely simmering, then add the raw king prawns. Poach the prawns until just pink and opaque — about 2–3 minutes depending on size.
Turn off the heat. Stir in the fish sauce and lime juice, then taste and adjust seasoning with a little salt or extra fish sauce/lime as needed. If you prefer a clearer presentation, fish out and discard the larger galangal slices and lemongrass stalks before serving.
Ladle the soup into warmed bowls and garnish with chopped fresh coriander and sliced spring onions. Serve immediately.
Tips
- Keep the heat gentle when infusing aromatics — boiling makes a cloudy, bitter broth.
- If you want a vegetarian version, swap chicken stock for vegetable stock and use soy sauce plus a strip of kombu for depth (see substitutions).
- Prepare the aromatics first and have everything to hand; prawns only need a couple of minutes so timing is crucial.
- Taste and adjust seasoning at the end — fish sauce, lime and palm sugar should be balanced, not overpowering.
- Leftovers keep for 24 hours in the fridge; reheat gently and add a splash of fresh lime before serving to revive the flavours.
Substitutions
raw king prawns → firm white fish fillets (e.g. cod or pollack), cut into large chunks, add at the same stage but allow 3–4 minutes to poach
Noticeably differentchicken stock → vegetable stock plus a small strip of kombu (dried kelp) for umami
Stays closepalm sugar → soft light brown sugar, same weight (15 g)
Stays closefish sauce → light soy sauce plus a pinch of seaweed powder or a little extra lime for depth
Noticeably different
Nutrition
Per serving · estimated
- 150
- Calories
- 24 g
- Protein
- 7 g
- Carbs
- 3 g
- Fat
- 2 g
- Fibre
- 4 g
- Sugar
- 1200 mg
- Sodium
FAQ
Can I make this soup without prawns?
Yes — use firm white fish (add a few minutes to poaching) or keep it vegetarian by using vegetable stock and replacing fish sauce with soy sauce plus a strip of kombu for umami.
Why is my tom yum cloudy?
Boiling the stock aggressively or overcooking proteins can cloud the broth. Keep to a gentle simmer when infusing and poach prawns briefly.
How spicy is this soup?
Heat comes from bird's-eye chillies — three gives a medium kick. Reduce to one or remove seeds to make it milder, or add more for extra heat.
Can I make the soup ahead?
You can make the broth and refrigerate it for up to 24 hours, but add prawns, fresh herbs and lime juice just before serving for best texture and brightness.
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