The scripts used by the SE Asia region vary greatly as do the languages. This section will deal with the somewhat related scripts of China, Japan, and Korea. I am no expert in these languages and do not speak any pf these languages. Any help by a native speaker or knowledgeable person would be appreciated. Thank you to Xinxin for providing me with much needed corrections.
Many mutually unintelligible dialects (or more correctly, languages) are spoken in China, but they are all written the same. So, the character for fish maybe pronounced 'chang' somewhere and 'yu' somewhere else, but they both mean fish. Every Chinese word then has a character or uses more than one character - that originally represents the concept but now represents the word and a phonetic element - these characters are called hanzi. So, two systems were developed to write Chinese phonetically to be "easier" for others. The most popular is called pinyin which uses the Roman script (English) to write Chinese words. A system called bopomofo also was developed - it uses it's own character set to write words phonetically using serparate consonants and vowels like in English. Bopomofo isn't used much beyond first of second grade in Taiwanese schools. So bopomofo works like an alphabet, not like a syllabary like in Japanese or, for the most part, Korean. Which brings us to our next topic. Japanese borrowed and slightly modified the Chinese hanzi and called them kanji. So, Japan also developed systems for writing words strictly by their sounds. Kana, as they called it, was developed in the 9th century. The two kinds of kana are hiragana and katakana. Hiragana is used to write native Japanese words and affixes to kanji - the script is cursive and flowing. While katakana is used to write foreign words and for emphasis. Katakana is more angular. Korean also borrowed Chinese characters and called them hancha or hanja. Korean developed their own script in the 1400's - called hangul. It is very simple in that the consonants and vowels combine in a regular fashion (you'll see what I mean). The limitation to katakana and hiragana is that each consonant is always followed by a vowel (except for 'n'). For example - there is no letter 't' by itself - it has to be 'ta', 'to', 'te', etc. So one could not exactly write the word 'boat' instead you would have to write bo-ta or bo-tsu or something like that. Enjoy!

Summary of writing systems:
Here is Bopomofo - the English equivalents are given like as in Pinyin - here are some pronounciation tips:
(I made the following chart myself - it is read in rows from left to right, then top to bottom. The last row did not appear in one source but did in another, so I put it seperate from the others. The 3 or 4 letters that are in a row are related by their sounds.)


Here is Hangul - the letter marked (? NG) is either pronounced as 'ng' or is silent and used when a vowel begins a word. Sounds are not exact like in English, so some letters are half way between like (K,G).


Here is Katakana - the order you read is for the most part is top to bottom, right to left. The unmarked columns show the vowel (either A, I, U, E, O, YA, YU, and YO) by itself (without a consonant). Sometimes a character's sound will be different than what's expected - follow the note given inside it's box. Notice at the bottom, when K combines with ya, you get kya, etc unless otherwise noted. The Y in parenthesis is just a reminder for those letters. Transcription is given in Romaji.
(I made this chart myself)

Here is Hiragana - all comments from Katakana apply. Does the hiragana "mi" look like a Devanagari "m" (just a coincidence)? Japanese did borrow something from Devanagari / Sanskrit - and that is the order of the vowels - the short vowels were just omitted.
(I made this chart myself)

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Scripts of Chian, Japan, & Korea Scripts of South East Asia The Persian Alphabet