This was the way things had been since their childhood as neighbors growing up on Serangoon Road, mainly because, coming from a Chinese-speaking family, Carol had always felt inferior to Eleanor, who was brought up speaking English first. (1.2.4)
Carol Tai, despite her honorary title Datin signifying her family's immense wealth, still feels she must show deference to someone who grew up speaking English first. Man, family background means a lot in this world.
In their world, you did not bring home some unknown girl unannounced. (1.4.16)
Shang Su Yi's family operates in its own world: even Astrid knows Nick's move to bring home Rachel unannounced will not go over well.
Nor would it be appropriate for Rachel to stay at his grandmother's house without her explicit invitation (1.8.13)
"Appropriate" makes us think of larger social cues and ethics, which underscores the world of social customs Shang Su Yi has maintained in her family.
"If he's Singaporean, I have a responsibility to make sure he's good enough for you!" (1.16.124)
There certainly is a custom of making sure someone's mate is "good enough" for them in Singapore. Nearly the entire novel hinges on it!
"Nicky, boys with proper manners do not ever ask questions like that. You do not ever ask people if they are rich or discuss matters concerning money." (1.17.47)
Nick was chastised by his aunt Victoria early in life, reinforcing the family's tradition of never talking about money.
How on earth Shang Su Yi ever allowed her son to marry one of those Sung girls, I will never understand, Winifred thought. (2.9.125)
The operative word in here is "allowed." This rich Singaporean society has a custom that reinforces a parent's authority to allow or prevent marriages in their families.
Dr. Gu held the well-burnished kettle high above the teapot and began pouring. "I love watching Dr. Gu do his tea ritual," Wye Mun said to his daughter quietly. "See how he pours the water from high up. This is known as xuan hu gao chong—'rinsing from an elevated pot.'" (2.16.19)
The tea ritual with Dr. Gu contrasts the other, more modern customs we see in the novel. This ritual is about working and waiting for the tea, rather than forcing it for the sake of doing things quickly.
People like Mrs. Lee were used to only one kind of Chinese wedding banquet—the kind that took place in the grand ballroom of a five-star hotel. (3.7.1)
There's a sense of "back in my day" amongst the elder Singaporean elite. The template fancy wedding is apparently one of the treasured traditions of the old ladies.
"This is all so unbelievably archaic. We're living in the twenty-first century, and Singapore is one of the most progressive countries on the planet. I can assure you Ah Ma doesn't feel the way she did thirty years ago."
"[…]You don't know how important bloodlines are to her." (3.11.47-3.11.48)
This archaic custom is central to the plot of this story, yet we don't have much indication why it's so important. What does Shang Su Yi know that we don't?
"By law, I could not have another, but my in-laws were desperate for a boy, a male heir who could carry on the family name. If we had lived in the countryside, they might have just abandoned or drowned the baby girl […] However, there was one loophole to the one-child rule: if your baby had a handicap, you were allowed to have another." (3.20.19)
Again, Kerry Chu puts all of Singapore into perspective by explaining Rachel's potential fate as a result of the one-child policy in China. We at Shmoop are not fans of "you only get one" policies, especially if we're talking morning bagels.