Thai Red Ruby made during sweet genius challenge

Thapthim Krop (Thai Red Ruby)

the red vibrant looking chestnut that resembles ruby.
This recipe is not hard to tackle if you follow the steps closely. The most challenging part of the recipe is to coat the red chestnut in tapioca starch evenly and get it to cook it well so you get the jelly and chewy exterior of the "ruby".
After leaving the chopped chestnut in the food dye water to absorb the red coloring, you need to drain it before coating them in the tapioca flour and there is no substitute for tapioca starch unfortunately. The chestnut needs to be wet in order to absorb the tapioca starch too. So after draining it, you should immediately place them in the tapioca flour for coating. If you prefer the chestnuts to have a more chewy texture, you can double coat them in tapioca starch.
When cooking them, remember that the water has to be boiling hot else the tapioca coating will fall off the chestnut if the water is not hot enough and it will result in lumpy and gluey "ruby".
Accompanied by a sweet coconut milk pandan scented sauce. This dish can be prepared earlier and assembled when required. You may even add in durian and jackfruits to go along!
Prep Time 15 mins
Cook Time 20 mins
Chill 45 mins
Course Dessert
Cuisine Thai
Servings 4 bowls
Calories 296 kcal


  • Pot
  • Mixing Bowl



  • 10 pieces Water Chestnut
  • 1 cup Tapioca Flour
  • 1/2 tsp Red Food Coloring

Coconut Broth

  • 200 ml Coconut Milk
  • 100 grams Sugar
  • 1 tsp Salt
  • 1 knot Pandan Leaf
  • 1/2 cup Water
  • 2 tbsp Pearl Sago


  • Using a 1/4 cup water, add in your red colouring and mix through. Then drop in peeled and diced (1cm cubes) water chestnut and let it sit for about 5 mins.
  • In a appropriate sized saucepan, add in the coconut milk, pandan leaves (in a knot), salt and sugar and bring to a simmer (not boil) and make sure the sugar has been dissolved. Let it chill down in the fridge to cold for service.
  • Bring another small saucepan to a raging boil, and add in your sago pearls and let it cook for approximately 4-5 mins or until the pearls almost translucent. Sieve through and run it under some water to chill it down to room temperature. Keep aside with a little water, so they don't stick.
  • Drain the water chestnuts, and with heat up 5 cups of water in a saucepan to a rolling boil, and cook through the sago for about 2 minutes. Drain and chill them to room temperature.
  • Coat them in the tapioca flour. And cook them in the boiling water again until the flour is cooked through. You can coat the chestnuts 2 or 3 times for desired thickness of the skin.
  • Finally, assembly time - the chestnuts and sago with the coconut broth can added into a appropriate serving bowl.


  1. Forward Preparation - You can prepare all the 3 components well ahead of time before service. Just note that cooked pearl sago and water chestnut do not refrigerate well and they are to be kept at room temperature.
  2. Sugar Type - Palm sugar is the order of the day, however you can switch it out for brown sugar or gula melaka. The flavours will vary with the type of sugar you use.
  3. 5 Cups of water - I tend to use alot of water when i'm boiling either the rubies or the pearl sago - this is the ensure that they have enough space to "swim" and cook rather than sticking to each other.
  4. Pandan - Extract or essence can be used in substitution, however, nothing beats the real thing.
  5. Coconut Broth - The longer the pandan sits (or simmers) with the coconut broth, more aromatics are infused into it. Purist will make the broth well ahead of time and let it rest to infused maximum flavours.
Keyword quick and easy

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