Hong Kong chefs always use Corn Starch, Potato Starch or Sweet Potato Starch for thickening in Chinese cooking. We normally call it (生粉) means raw flour/starch.

Corn Starch

Sweet Potato is not the potato that you add the sugar with.

Sweet Potato

Sweet Potato Starch

The sweet potato or kumara (Ipomoea batatas) is a dicotyledonous plant that belongs to the family Convolvulaceae.

source from Wikipedia.

Potato

Potato Starch

Starch from Corn, Potato or Sweet Potato depends on different brand and manufacturing process, they will have different taste and stickiness, therefore you must actually try it and alter the quantity that's fit your recipe the best.

經我數日來不斷研究，最後發覺好多因為唔係香港人嘅人寫到香港生粉又係粟米粉、太白粉、木薯粉，最後搵到多年經驗香港廚師留言:
"生粉是可以分為粟米粉和蕃薯粉兩種.生粉是在香港飲食文化中所稱呼.因為經濟上的問題,很多餐廳和酒家都是用蕃薯粉比較多,用來平常的餸菜勾芡或者是醃肉都是用它.

生粉：
又名豆粉或馬鈴薯澱粉，多來自荷蘭或德國，酒樓食店多用荷蘭風車牌，多用作打芡或做點心餃皮之類，於少量雜貨舖才有家庭裝售賣。

鷹粟粉是一個牌子的粟米粉,通常用來做一些榚點時會用到它,因為做出來的時候會比較滑."

[其實生粉可是統稱，澱粉也是統稱]

香港廚師常用生粉亦有熟粉，生的未煮熟，熟的可以生食，例如熟玉米粉、熟太白粉、熟糯米粉是糕粉的一種。

Q: 玉米粉可以生吃嗎?
A: 玉米可以生吃嗎? 可以；玉米粉照道理可以生吃。

Q: 太白粉可以生吃嗎?
A: 太白粉是由馬鈴薯(香港叫薯仔)制成，你會生吃嗎，我唔會囉。

Q: 那麼熟玉米粉、熟太白粉、熟糯米粉在哪裡買?
A: 只要將玉米粉放入鍋內以小火翻炒，炒至有香味就是熟玉米粉；自製熟太白粉，很簡單~~ 將太白粉放進烤箱低溫烘烤就是熟太白粉了，或是在炒菜鍋裡小火炒熟，至於時間就看量斟酌了。 記得一定要用低溫要不然太白粉很會就會焦黃，另外容器也不可有水或油，要不然就會變成麵糊了。熟糯米粉的做法：用微波爐大火high heat 叮1分鐘，或用鑊不落油小火炒熟，即成。

生粉 source from:
http://hk.apple.nextmedia.com/supplement/food/art/20080216/10756987

How To Make Starch (Wet Tapioca) From Cassava

Tapioca Starch 木薯粉 

If you are not sure what is the flour/starch, just taste if or stir with water to cook it. Tapioca Starch is clear and jelly-like and chewy after cooked.

After stir fry with low heat, and that's look like a chewy gum.

Show you how to make it at home start from scratch.

If you think it is taking too much time and effort to do it , then simply buy it in your store. We have so many choices in Thailand or any supermarkets in Asia.

Don't look at the brand, but buy different one to test and feel which one you like the most.

Tapioca in Thailand มันสำปะหลัง

This is the new packing with photo that I like the most, easy to remember.

In Hong Kong, we call Tapioca Starch as "生粉/木薯粉", Taiwan use this to make the most famous bubble milk tea.

Those Tapioca pearls are made with Tapioca Starch.

Pearl tapioca is a common ingredient in South, East and Southeast Asian desserts such as falooda, kolak, sago soup, and in sweet drinks such as bubble tea, fruit slush and taho, where they provide a chewy contrast to the sweetness and texture of the drink. Small pearls are preferred for use in puddings. In Brazil, the pearls are cooked with wine or other liquid to add flavor and are called sagu.

In some recipes, the ratios using Rice Flour vs Tapioca Starch may be from 2:8 to 5:5 in ratio in making HK Bowl Rice Pudding.

在東南亞，木薯比薯仔便宜，木薯粉是阿媽用來勾茨的澱粉，通常都叫泰國生粉/木薯粉 

Tapioca Starch.

泰國生粉係木薯嘅澱粉，煮中餐時用到佢嚟打芡，令餸菜嘅汁液變得杰啲。

台灣人喜歡用太白粉，太白粉加水遇熱會凝結成透明的粘稠狀，使湯汁看起來杰些，同時使食物外表看起來有光澤。要謹記太白粉不能直接加熱水，否則會立即凝結成塊而無法煮散。食物放涼之後，茨汁會變得較稀，因此一般整蛋糕/做西點多利用粟粉來達到粘稠的特性而不使用太白粉。 

Flour for Thickening only?
Most people learn that rice flour and all purpose flour both work well as thickening agents for soups, sauces and gravies. Both are suitable for making roux and slurry-thickened sauces and can be used interchangeably in recipes calling for either.

We are here to tell you that our Asian diet is mainly using "Rice" and we can make Chinese Cake called: Glutinous Rice Pudding with Red Beans which with the suggestion from our department of health as "Diabetes-Friendly Recipes". If you are not sure what kind of Chinese herbs was that, then actually you can try the Chinese Diets, we also use the good common herbs such as "dried tangerine peel" (should be 5 years naturally dried) to get a healthy body.

Chinese or most Asian are thin because rice is the major diet in old days, not until we start learning to make cake, bread and drinking milk when western food met Asian food.

Or we make Rice Cake called: Making HK White Sugar Sponge Cake

Is rice always Gluten-Free?

In most cases, yes: rice is gluten-free. Plain rice — regardless of whether it's whole-grain brown rice, polished white rice, long-grained basmati rice or even exotic black rice — is always considered gluten-free, assuming it's been protected from gluten cross-contamination in processing and cooking. (I share more about the safest brands of rice below.)

But you need to beware of flavored rice mixes, since these can contain gluten ingredients, and often do.

Surprisingly, the type of rice called glutinous rice, also known as sticky rice or sweet rice, is gluten-free. Despite the name, it doesn't contain the form of gluten that's dangerous to those of us with celiac disease or non-celiac gluten sensitivity; the term "glutinous" simply refers to the fact that glutinous rice gets glue-like, or sticky, when cooked.

source from: https://www.verywell.com/is-rice-gluten-free-562773
By Jane Anderson - Reviewed by a board-certified physician.

Rice Flour is different with Rice Starch

Mostly we use for the thickening in Hong Kong called Corn Starch.

Rice flour (also rice powder) is a form of flour made from finely milled rice. It is distinct from rice starch, which is usually produced by steeping rice in lye.

Rice flour is a particularly good substitute for wheat flour, which causes irritation in the digestive systems of those who are gluten-intolerant.

Rice flour is also used as a thickening agent in recipes that are refrigerated or frozen since it inhibits liquid separation.

So, where can you buy Rice Flour in your country, I find that in US is pretty dominant for only 5 brands. In Asia, you have lots of choices, most rice seller at least provide you 5~10 types even in jasmine rice only, exclude the Glutinous Rice.
However, I just tell you that you can make your own Rice Flour at home, if you subscribe my newsletter. haha.

When I am talking about choosing rice, I am a very choosy person and need to smell it, look at it shiny without white spot. Thus I almost pay the most expensive one from my selection. There are new rice and old rice, the new one is better when you make the congee.

The most common one we use for HK snacks are:
Rice Flour 粘米粉 and Glutinous Rice Flour 糯米粉 , you will need to mix accordingly and I will explain them their characteristic in later chapters.

The Red color is Rice Flour and Green color is Glutinous Rice Flour for this brand, it is famous, but not the best and I found there are some fake selling in China too.
Thailand has very good reputation making both of them in many different brands, you should try yourself until which one satisfy you most.

Rice Flour 粘米粉 แป้งข้าวเจ้า
Glutinous Rice Flour 糯米粉 แป้งข้าวเหนียว

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Thumb Up to Department of Health of Hong Kong!

I was surprised tonight to find out the recipe from Department of Health, thus I would like to share with all of you.

Glutinous Rice Pudding with Red Beans (10 pieces)
(Source of recipe: dietitian of the Department of Health)
Ingredients:
Rice flour 75 g (2/3 cup)
Brown sugar 60 g
Red bean 2 tbsp (dried)
Dried tangerine peel 1 pc
Water 4 cups (960 ml)
Vegetable oil 1 tsp

Method:
Rinse and soak the red beans for about an hour. Put the red beans and dried tangerine peel in 3 cups (720 ml) of water and boil under low heat for about an hour until soften. Drain the red beans and discard the tangerine peel.
Mix the flour with ½ cup (120 ml) of water to form a batter.
Boil ½ cup (120 ml) of water and then add in the sugar and boil until it dissolves.
Add in the sugar water to the batter and mix well. Add in the red beans and oil and mix thoroughly.
Prepare 10 small bowls in a steamer. Evenly pour the mixture into each bowl and steam under high heat for about 20 minutes or until the puddings are cooked.

source from: http://www.pco.gov.hk/tc_chi/resource/recipes/recipes_snacks_05.html

I remember I fly with Canadian airline, there was a little bun on the dish, and I tried to use the metal knife cut it into half, thus I could spread the butter on it. However, you should know the knife was blunt on the plane and the bread was so hard and I failed even try to punch into it. I asked my Canadian friend why the bread was so hard and he replied: "It's good for your teeth!".

That's was a good lesson, I understand now rice is Chinese main dietary, thus western people use wheat flour to make bread and we use rice flour to make our White Sugar Sponge Cake.

The trick to this HK White Sugar Sponge Cake of course is getting it to be wobbly and holey.  This is where the rise of the flour mix is all important.  (I tried another recipe before this one and got a half risen cake that went in the trash bin.)  You want to have the cake honeycombed and wonderfully wobbly and squeezable all the way through.

Here is the nice presentation of how to make White Sugar Sponge Cake:

Published on May 6, 2014

By popular demand, dino PJs this weekend! White Sugar Sponge Cake is a deceptively simple dessert with far more flavour than one would expect. It's a yeast-raised steamed rice cake that's apparently quite popular. The yeast serves to provide a complex flavour through fermentation and creates an interesting texture as the carbon dioxide bubbles get trapped by the cooking cake.

You can steam it in a bamboo steamer lined with parchment paper, if you have it, or you can make an improvised steamer by balancing a cake pan on something in a large pot, to keep it out of the water.

190 g Rice flour, sifted

160 g White sugar

8 g Active dry yeast