"loh" = surprising or positive statement, "I already bought that book!" Loh, aku sudah beli buku itu. ^^^^^ You also can place "Loh" in the end of the statement "I already bought that book!" ==? "Aku sudah beli buku itu, loh"

"loh" suprising word can mean positive or negative statement depend the sentences ex : "Loh.. seharusnya tidak seperti ini" ( negative, this sentence can be interpreted about disapointed about something ) "kok" like you said it can used for emphasize question or used after word " loh " .. ex : Loh.. kok jadi seperti ini? / Loh.. kok kamu tidak pergi ke sekolah? "wah" is suprising word too like " loh " both is almost same meaning and can used in positive,negative or question sentences.. All that words is slang used in in formal conversation... Semoga ini membantu :)