Indonesian is written the way it sounds. Once you know the letters, you never have to guess, and you never have to learn a spelling separately from a pronunciation. That alone puts it ahead of English, French and every tonal language in Asia.
Five letters behave differently from English. That is the entire list.
c is always “ch”
cabai ‘chilli’
cantik ‘beautiful’
kucing ‘cat’
Never “k”, never “s”. English speakers reach for one or the other and are simply not understood.
ng is one sound, not two
The trap is that English has both versions and spells them the same. In singer the g is silent; in finger you hear it. Indonesian always uses the singer version.
bunga ‘flower’
dengan ‘with’
It also appears at the start of words, which English never does. ngomong ‘to talk’ begins with the sound that ends sing. Practise by saying “sing” and then dropping the “si”.
ny is the sound in canyon
nyamuk ‘mosquito’
nyanyi ‘to sing’
r is rolled
A short tap of the tongue, closer to Spanish than to English. An English r is understood but marks you instantly as a foreigner.
rumah ‘house’
berapa ‘how much’
Vowels stay pure
This is the one that catches people who think they have it right. English glides its vowels: “no” is really “no-oo”. Indonesian vowels are single, short and clean.
kopi ‘coffee’ ends in a clean “ee”, not “ee-uh”
satu ‘one’ ends in a clean “oo”
And the h you can hear
A final h is not silent. It is a soft breath out.
rumah ‘house’
mudah ‘easy’
Drop it and mudah ‘easy’ starts to sound like muda ‘young’.
That is the whole system. The only letter left to worry about is e, which has two values, and that gets its own lesson.