General note: All the 'lah', 'leh', 'oi', 'har', 'aiya', etc. added to the dialogue are part of the Singlish vocabulary to accentuate the meaning of the sentence.
A levels: An examination held annually in Singapore, conducted jointly by Singapore's Ministry of Education and the University of Cambridge.
ACS: Anglo-Chinese School, one of Singapore's top high schools.
Chiarong, or 佳容: Chloe's Chinese name. The first character means "good, auspicious, beautiful" while the second means "appearance, form". So essentially, a good and beautiful girl.
Chio: Pretty in Hokkien.
Chiobu: Pretty girl in Hokkien.
CCA: Co-curricular activity. Used to be known as extracurricular activity, but the name is changed in Singapore. It's a non-academic activity that is required for all students to undertake as part of their education.
EC: eye candy. Meaning: someone you find superficially attractive to look at, but not necessarily crushing or interested romantically. It's a Singaporean slang used among Junior College students. It can also be used as a verb.
Example usage 1: "Who is your EC?" "Jon!"
Example usage 2: "Omg let me tell you a secret... I EC Jon."
HDB: Housing Development Board, Singapore's public housing. They are subsidized housing built and managed by the government.
Hokkien: A common Chinese dialect spoken in Singapore
Hyuna: Popular solo artist in South Korea.
Is it?: A variation of "Really?" Usually appended to a sentence.
Jay Chou: Jay Chou is the king of MandoPop.
JC: Junior College. High school equivalent in Singapore.
One: Sometimes added to the end of a sentence to emphasize it. It has Mandarin roots to it, and a Reddit discussion is linked in the comments -->
Siao: Crazy in Hokkien.
Wah lao: A Hokkien curse word commonly used.