yes. "ape" ussually used for a friend.

....

Use this as a metaphor 안녕하세요 = Apa 안녕 = Ape/Pe <--- Something that we cut it off and it is a 반말.. Similar goes to Kenapa --> Knape

Ape는 말할때만 사용하는데 Apa는 쓸때 사용하는 것이예요... 이것은 사투리인데 어디는지 사람이 사용하고 있어요.. Apa는 뉴스밖에 사용하지 않을 것 같아요.. 다른 보기 bila --> bile kenapa --> kenape mana --> mane 대부분 마지막 단어 'a'가 있으면 'e'로 빠꿀거예요..

the reason why the are spelled differently is because they 'sound' different.. you know.. they got the same meaning.. saying sa-ya , a-pa in malay is what we call 'bahasa baku' we don't use bahasa baku in our daily lives.. it's really hard actually to find someone who use it (bahasa baku) nowadays.. so most of the words that end with the vocal 'a' often mention as 'e' like.. saya, we pronounce as saye, (informal-not using bahasa baku) same goes to apa,mana,ada and etc..