Thai Soups Explained: From Tom Yum to Gaeng Jued

Outside Thailand, Thai soup usually means tom yum or tom kha, served in a bowl of its own before the main course. In Thailand, soup is something different. It sits on the table with everything else, shared from one pot, and it ranges from fiery and sour to so mild it is almost plain.

Understanding the main kinds, and the job each one does in a meal, makes it much easier to cook them well. It also explains why a gentle clear soup is just as important to a Thai table as the famous hot and sour ones.

Tom, gaeng and the words on the menu

Tom means to boil, and dishes that start with tom are usually soups simmered with fresh aromatics rather than a pounded paste. Gaeng is often translated as curry, but it covers a wide family of liquid dishes, some thick with coconut milk, some thin and soupy. Gaeng jued, gaeng som and gaeng lueang are all called gaeng, yet they eat more like soups than the curries many people picture.

Tom yum: clear or creamy

Tom yum is a hot and sour soup, most often made with prawns (tom yum goong), and sometimes with chicken, fish or mixed seafood. The broth is perfumed with lemongrass, galangal and makrut lime leaves, sharpened with lime juice, seasoned with fish sauce and lifted with bird's eye chillies. Straw mushrooms are the traditional vegetable.

It comes in two main styles:

Tom yum nam sai: the clear version. The broth stays translucent and the flavours are bright, sharp and clean.
Tom yum nam khon: the creamy version. Evaporated milk or coconut milk is stirred in, often with a spoonful of nam prik pao, the roasted chilli jam, which gives the soup its orange colour, a little sweetness and a deeper, rounder heat.

Neither is more correct. Many cooks and diners have a strong preference, and restaurants in Thailand commonly offer both.

Tom kha: the coconut soup

Kha is the Thai word for galangal, which tells you what leads in tom kha. It uses the same aromatics as tom yum, but in a broth of coconut milk, so the result is rich, gently sour and fragrant rather than sharp. Tom kha gai, with chicken, is the best known, and mushroom versions are common.

The coconut milk should be heated gently and not boiled hard, which can make it split and grainy. Tom kha is usually less hot than tom yum, and it is often balanced with a touch more sugar.

Gaeng jued: the quiet soup

Jued means bland or mild, and gaeng jued is the soup most Thai families eat most often. It is a clear broth, usually pork or chicken, seasoned simply with fish sauce or light soy sauce, white pepper and garlic, often with coriander root simmered in it. Common versions include:

Gaeng jued tao hu moo sap: soft tofu and minced pork, sometimes with seaweed.
Gaeng jued woon sen: glass noodles with minced pork and vegetables.
Gaeng jued fak: winter melon, cooked until soft and almost translucent.
Gaeng jued with cabbage, mushrooms or pork balls, depending on the market.

It is the soup made for children, for anyone feeling unwell, and for the side of a meal that is otherwise loud. Its job is to calm and refresh, and it does that well.

Sour curries and regional soups

Gaeng som is a sour curry with a thin, soupy broth. The central Thai version is made with a paste of dried chillies, shallots and shrimp paste, soured with tamarind, and cooked with fish or prawns and vegetables such as green papaya, cabbage or long beans. It has no coconut milk and is sharp, hot and savoury.

In the south, gaeng som usually means a related dish also called gaeng lueang, the yellow curry, coloured and flavoured with fresh turmeric. It is fiercely hot and sour, and it is one of the region's everyday dishes, typically made with fish.

Tom saep is the northeastern hot and sour soup, often made with pork ribs, beef or offal. It shares the lemongrass, galangal and lime of tom yum, but adds roasted chilli and fresh herbs such as sawtooth coriander, sometimes with a spoonful of toasted rice, so it tastes earthier and more herbal.

Tom khlong is an older central Thai soup, sour and smoky. It uses tamarind or other sour fruit, roasted dried chillies and grilled shallots, and is often made with dried or smoked fish. It is less common on restaurant menus than tom yum but well worth seeking out.

Khao tom, rice simmered in a clear broth, sits at the gentle end of the scale. It is usually a meal on its own, eaten in the morning or late at night, rather than one soup among several.

How soup fits into a shared meal

In a Thai meal, soup is not a course. It arrives with the other dishes and is placed in the middle of the table, often with its own serving spoon, and everyone takes a little at a time into a small bowl or straight onto their rice. Diners go back to it throughout the meal, using it to cool down after something hot or to add moisture to rice.

That changes how a soup should be judged. A tom yum served alongside a mild stir-fry and an omelette can be bold. A meal with a fiery salad and a curry is better served by a gaeng jued. When planning a meal, choose the soup to contrast with the rest of the table.

Aromatics and seasoning: what goes in when

The aromatics are there to flavour the broth. They are cut in large pieces, and diners usually leave them in the bowl rather than eating them.

Lemongrass: trim the root and the dry tops, then bruise the stalk with the back of a knife or a pestle and cut it into short lengths so it releases its oils.
Galangal: slice into thin rounds. It is too hard to eat, but it gives up its flavour well in simmering liquid.
Makrut lime leaves: tear them, removing the central rib if it is tough, so their fragrance gets into the broth.
Chillies: bruise bird's eye chillies lightly so they release heat without breaking apart.

Add the aromatics to simmering stock and give them a few minutes before the main ingredient goes in. Prawns and fish need only a minute or two. Season with fish sauce during cooking, then taste.

Lime goes in last. Boiling dulls lime juice and can make it bitter, so many cooks turn off the heat, then add the lime, or squeeze it into the serving bowl and pour the hot soup over it. Taste once more after the lime is in, as it changes how the salt reads, and adjust with a little more fish sauce if needed. The finished soup should taste fresh, with the sour and the heat arriving together.