Indonesian letters are the same as the ones used in English. All letters a through z are used, and no other letters are used. Of course, they are pronounced differently. However, unlike English, Indonesian letters are pronounced much more consistently and no letters are muted. You will find that the pronunciation is much closer to Spanish.
Below is a table of Indonesian alphabet. The pronunciation column shows how we pronounce the letter in Indonesian. The sound column shows how it sounds in English. If there are no notes in the sound column, it is roughly the same as English.
Listen to how Indonesian pronounce their alphabets: A-M; N-Z
a (like a in father)
always the a in father, bath but shorter, never the "a" in catch
be (like ba in bay)
[ʨ] (versus English [ʧ])
Almost always like the ch in church, chest, and in some borrowed words or proper nouns like the French c'est (nearly like English say)
de (like da in day)
like de in deli
[ɛ], [ə], [e] (not [eɪ])
there are three ways of pronouncing e in Indonesian: