When I was a kid, my English teacher started with teaching Phonetic Symbols, I did not really notice or even knew the reason why I had to study such things; plus it was hard for an eight year old kid to start with such things.
So, I could not remember them well and ended up noting the pronunciation of English word in Khmer. It worked! However, I had to struggle remembering Khmer pronunciation; and the sound was not as accurate as a native speaker and might result in being unable to deliver the meaning to our partner.
I did learn about the Sh Ch part. It was pretty easy to produce such sound, but I did not learn about that there are two types of sound of EA, AU, OW, etc. You know what I’m saying? Probably not! 
Because shamefully, I have just learned more of Phonics when I first started my first job as an English teacher of a Young Learner Program at New World Institute. I never thought that knowing Phonics could be that wonderful.
I am not going to tell you all that in details. However, I could illustrate some which will brighten your eyes a bit.
Let say, BOW. That is the hard sound of OW, while COW, TOWEL, we use the soft sound of OW. See the difference? Or it could be seen through THREAT and EAT. Could you notice the difference between the soft sound and the hard one?
More examples, people might not notice that with a magic E, words could be pronounced interestingly as it will follow the original sound of the vowel. You will know what I mean after reading below.
For example, letter A. The sound is supposed to be A just like the letter, however, it is not. You need to add an E to get the original sound of the A.
If not, the sound will become AE. For example, CAT. If you add an E, the sound will be an original sound like KATE. So much A that you could hear.
It also applies to other vowels as well; for example, COPE, KITE, PETE, CUBE. As you can see, without an E, the sound of this word would not be so original. You can find all of these information in Phonics book.
In summary, it is important for us to learn the concept so that we could pronounce each word correctly. You may find that Phonics book at New World Institute and do some self-learning, or probably just download some from the internet.
