Tom kha gai is the soup that made me fall for Thai food: coconut milk simmered with lemongrass, galangal, and makrut lime leaves until it smells like a spa, then finished with chicken, mushrooms, and a bright squeeze of lime. The only problem is standing at the stove to babysit it. This slow cooker version fixes that entirely.
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Everything goes into the crockpot in the morning, and by dinner the broth has quietly absorbed all that aromatics while the chicken turns fork-tender. You do the finishing touches at the end, because lime juice and fish sauce should never cook for hours, and that is what keeps the soup tasting fresh instead of flat.
If you have ever ordered tom kha at a restaurant and wondered why yours never tastes the same, it is usually the aromatics and the balance of salty, sour, sweet, and rich. This recipe nails all four, and it reheats beautifully for lunches all week.
Why You'll Love This Recipe
About the Ingredients
1 1/2 lb (680g) boneless, skinless chicken thighs, cut into 1-inch pieces
Thighs stay juicy after hours of cooking, where breast can turn stringy. If you only have chicken breast, add it in the last 90 minutes on Low instead of at the start.
2 cans (13.5 oz / 400ml each) full-fat coconut milk
Full-fat is essential for body; light coconut milk makes a thin, watery soup. Shake the cans well before opening, or whisk the separated cream back in.
4 cups (950ml) low-sodium chicken broth
Use a good-quality broth since it is the backbone of the soup. Vegetable broth works for a lighter version, but add an extra tablespoon of fish sauce to compensate.
8 oz (225g) cremini mushrooms, sliced
Cremini holds its shape better than white buttons in a slow cooker. Oyster mushrooms are a lovely upgrade and give a silkier texture.
3 stalks lemongrass, tough outer layers removed, cut into 2-inch pieces and smashed
Smashing releases the oils; leave the pieces large so they are easy to fish out. Lemongrass paste (2 tablespoons) is a fine shortcut but will cloud the broth.
1 piece (2-inch) fresh galangal, sliced thin (or 8 dried slices)
Galangal is sharper and more piney than ginger; do not swap in ginger if you can help it. If unavailable, use 1 tablespoon of tom kha paste plus 1 teaspoon grated ginger.
6 makrut lime leaves, torn (or 1 tablespoon lime zest)
Tearing the leaves releases the citrus oils; remove them before serving since they are tough. Frozen makrut leaves are sold at most Asian markets and keep for months.
3 tablespoons fish sauce, plus more to taste
Three Crabs or Red Boat brand gives the cleanest flavor. Soy sauce or coconut aminos can replace it for a vegetarian pot, though the flavor will be less deep.
1 tablespoon palm sugar (or light brown sugar)
Palm sugar rounds out the sour and salty notes; brown sugar is a close stand-in. Start with half and taste, since coconut milk varies in sweetness.
8 oz (225g) cherry tomatoes, halved
Added near the end so they keep their shape and brightness. Quartered roma tomatoes work but will break down more.
3 tablespoons fresh lime juice (about 2 limes)
Always add lime off the heat; boiling makes it taste bitter and dull. Bottled lime juice is a last resort only.
1/4 cup chopped fresh cilantro and 1 sliced Thai chili, to serve
Cilantro and chili go in at the table so they stay fresh and fragrant. Thai basil is a great alternative if you are not a cilantro person.
Tips & Tricks
Do not boil the coconut milk
Slow cookers on High can push coconut milk to a rolling simmer, which makes it split and look curdled. Keep it on Low or stir it in near the end.
Fish out the aromatics
Lemongrass, galangal, and lime leaves are not meant to be eaten and are unpleasant to bite into. Fish them out with tongs before serving, or tie them in cheesecloth for easy removal.
Season at the end, not the start
Fish sauce and lime juice added at the beginning cook off and taste flat. Add both after the slow cooker is off, then taste and adjust.
Do not overcook the chicken
Even thighs get mushy past 8 hours on Low. Aim for 4 to 6 hours on Low, or 2 to 3 hours on High, and check at the earlier mark.
Pro Tips
Step-by-Step Instructions
1. Prep the aromatics
Smash the lemongrass stalks with the flat of a knife and thinly slice the galangal. Tear the makrut lime leaves in half so the citrus oils can escape into the broth.
2. Layer the slow cooker
Add the chicken thighs, mushrooms, lemongrass, galangal, and lime leaves to a 6-quart slow cooker. Pour in the chicken broth and 1 1/2 cans of the coconut milk, reserving the remaining half can for the finish.
3. Slow cook on Low
Cover and cook on Low for 5 to 6 hours or on High for 2 1/2 to 3 hours, until the chicken shreds easily with a fork and reads 165F (74C) on an instant-read thermometer. The broth should be gently steaming, never at a rolling boil.
4. Add the tomatoes
Stir in the cherry tomatoes during the last 20 minutes of cooking so they soften slightly but keep their shape. If you are cooking on High, add them in the last 10 minutes.
5. Remove the aromatics
Turn off the slow cooker and use tongs to fish out the lemongrass, galangal, and lime leaves, pressing them against the side of the pot to release any broth. Discard them.
6. Finish the broth
Stir in the reserved coconut milk, fish sauce, palm sugar, and lime juice. Taste and adjust: more fish sauce for salt, more lime for brightness, more sugar for roundness. The broth should taste bright and rich, with a gentle sour edge.
7. Serve hot
Ladle into bowls and top with cilantro and sliced Thai chili. Serve with jasmine rice or on its own, and pass extra lime wedges at the table.
Delicious Variations
Shrimp Tom Kha
Swap the chicken for 1 lb of large shrimp added in the last 10 minutes of cooking; they are done when pink and curled.
Vegetarian Tom Kha
Use vegetable broth and soy sauce instead of fish sauce, and add 8 oz of firm tofu cubes in the last 30 minutes.
Extra Veggie Tom Kha
Add 1 cup of sliced bell pepper and 1 cup of snow peas with the tomatoes for crunch and color.
How to Store Slow Cooker Tom Kha Soup (Thai Coconut Chicken Soup)
Refrigerator
Store in an airtight container in the refrigerator for up to 4 days. The coconut milk may separate; whisk gently while reheating.
Freezer
Freeze in portions for up to 2 months, but leave out the cilantro and lime. Coconut milk can turn grainy after freezing, so whisk vigorously once thawed.
Reheating
Reheat gently over medium-low heat (about 300F/150C on the stovetop setting) until steaming, about 5 minutes, without boiling. Add a fresh squeeze of lime after reheating.
Frequently Asked Questions
Q: Can I use chicken breast instead of thighs in tom kha soup?
Yes, but add it later so it does not dry out. Cube the breast and stir it in during the last 90 minutes on Low or 45 minutes on High, until it reaches 165F (74C).
Q: Why did my coconut milk curdle in the slow cooker?
Coconut milk curdles when it boils, which happens easily on the High setting. Cook on Low, avoid stirring too aggressively, and stir in the final half can of coconut milk off the heat to restore a smooth texture.
Q: What can I use instead of galangal and lemongrass?
Tom kha paste is the best substitute and is sold at Asian markets; use 2 tablespoons in place of both. In a pinch, use 1 tablespoon grated ginger plus 1 tablespoon lime zest, though the flavor will be less authentic.
Q: Is tom kha soup spicy?
No, tom kha is mild and creamy, not spicy. The heat comes only from the sliced Thai chili garnish, so leave it out or serve it on the side for anyone who wants less heat.
Q: Can I make this tom kha soup on the stovetop instead?
Yes, simmer the broth, aromatics, and chicken in a pot for 25 minutes over medium heat, then add the coconut milk, mushrooms, and tomatoes and simmer 10 more minutes. Finish with fish sauce, sugar, and lime off the heat.
If you make this slow cooker tom kha soup, I would love to hear how it turned out. Snap a photo of your bowl and tag me on social, or leave a comment below with the tweaks you made. It is the kind of recipe that gets better every time you make it.
Slow Cooker Tom Kha Soup (Thai Coconut Chicken Soup)
This slow cooker tom kha soup is creamy Thai coconut chicken soup made hands-off, with lemongrass, galangal, and lime for a bright, cozy bowl.
🧂 Ingredients
- 1 1/2 lb (680g) boneless, skinless chicken thighs, cut into 1-inch pieces
- 2 cans (13.5 oz / 400ml each) full-fat coconut milk
- 4 cups (950ml) low-sodium chicken broth
- 8 oz (225g) cremini mushrooms, sliced
- 3 stalks lemongrass, tough outer layers removed, cut into 2-inch pieces and smashed
- 1 piece (2-inch) fresh galangal, sliced thin (or 8 dried slices)
- 6 makrut lime leaves, torn (or 1 tablespoon lime zest)
- 3 tablespoons fish sauce, plus more to taste
- 1 tablespoon palm sugar (or light brown sugar)
- 8 oz (225g) cherry tomatoes, halved
- 3 tablespoons fresh lime juice (about 2 limes)
- 1/4 cup chopped fresh cilantro and 1 sliced Thai chili, to serve
📋 Instructions
- 1Prep the aromatics — Smash the lemongrass stalks with the flat of a knife and thinly slice the galangal. Tear the makrut lime leaves in half so the citrus oils can escape into the broth.
- 2Layer the slow cooker — Add the chicken thighs, mushrooms, lemongrass, galangal, and lime leaves to a 6-quart slow cooker. Pour in the chicken broth and 1 1/2 cans of the coconut milk, reserving the remaining half can for the finish.
- 3Slow cook on Low — Cover and cook on Low for 5 to 6 hours or on High for 2 1/2 to 3 hours, until the chicken shreds easily with a fork and reads 165F (74C) on an instant-read thermometer. The broth should be gently steaming, never at a rolling boil.
- 4Add the tomatoes — Stir in the cherry tomatoes during the last 20 minutes of cooking so they soften slightly but keep their shape. If you are cooking on High, add them in the last 10 minutes.
- 5Remove the aromatics — Turn off the slow cooker and use tongs to fish out the lemongrass, galangal, and lime leaves, pressing them against the side of the pot to release any broth. Discard them.
- 6Finish the broth — Stir in the reserved coconut milk, fish sauce, palm sugar, and lime juice. Taste and adjust: more fish sauce for salt, more lime for brightness, more sugar for roundness. The broth should taste bright and rich, with a gentle sour edge.
- 7Serve hot — Ladle into bowls and top with cilantro and sliced Thai chili. Serve with jasmine rice or on its own, and pass extra lime wedges at the table.
