A hot and sour broth scented with lemongrass, galangal and lime leaf, sharpened with lime and fish sauce — usually with prawns.
What makes it tom yum
Lemongrass, galangal and lime leaf, bruised, not eaten.
Lime juice added off the heat, so it stays bright.
Fish sauce and chilli to balance.
Where it comes from
Tom means boiled; yum, mixed — the same word as for Thai salads. The clear version, nam sai, is the older one; the creamier nam khon, with evaporated milk or chilli jam, is a Bangkok favourite. Tom yum kung was added to UNESCO's list of intangible cultural heritage in 2024.
How it varies
Nam sai
Clear, sharp and hot.
Nam khon
Creamy, with milk or roasted chilli paste.
Tom kha
Its gentler cousin, with coconut milk and galangal leading.