Because he wasn't able to express himself, he sometimes became frustrated and hit other children. Living in Los Angeles at the time, Chai sought help. The first step was to test for autism, and then check his hearing; both tests were negative.
Her son was 3½ before he was diagnosed with speech delay, and six months later he started speech therapy. Chai also did a lot of her own research. Now eight years old, his speech development is much improved. But it has been a long journey. When the family moved to Hong Kong 2½ years ago, she had to seek out a new set of professionals to help.
"There is more awareness about these issues in the US. I took him to preschool, and after one day, they were already giving me feedback on what he needed. In Hong Kong, it's hard for parents to know about their child's development, and whether they have a need or a problem," says Chai.
Sam Pygall, a British-trained speech and language therapist, understands the Hong Kong environment and its unique set of pressures. Raised in Hong Kong, she went to the Britain to study. After a decade working with both the health and education authorities there, she returned to Hong Kong in 2002.
"Hong Kong is a very high-pressure place. It's difficult for a parent to figure out what's normal for a two year old, and to also to accept that there is a range of normal," says Pygall.
Speech development begins long before a child utters its first word. Ideally, a baby will be babbling soon after it is born, and making noises and crying when it is hungry or when its mother leaves the room.
First words are expected at about 12 months, although these will often be unrecognisable without taking note of the context: parents understand the child is saying "ball", only because he is pointing at one.
"By two years, we expect them to be putting two words together, and by three years, they should be putting three or more words together in sentences," says Pygall. Signs that something might be amiss are noticeable early on, and the sooner they are dealt with the better. If a child is not babbling by the time it's a year old, that is something to be concerned about, says Pygall.
The first thing to look at is feeding. Check to see everything is working as it should be. What kind of food the child is having, what they are doing with their food, and are they keeping it in their mouth?
"It's about sensory experiences and muscular experiences. These include the way that we feed them, and the different textures we feed them. They are important in terms of the way that speech and language begin. Children need to have these experiences," Pygall says.
Chai had this checked in the US. "The occupational therapist thought that he had sensory reintegration issues, and suspected the central auditory processing [was at fault]. That connects the sounds and the process in the brain that translates it into language," says Chai.
Pygall also examines the child's home environment, to find out whether it's a noisy or quiet house, and to learn about the personalities of the people surrounding the child. A quiet mother will sometimes mean a quiet child, but if the child remains quiet, she suggests checking his or her hearing.
A study by researchers at the University of Washington and University of Connecticut showed that what promotes language development isn't so much the quantity of words, as the style of speech and the social context in which it happens.
Simply put, the more parents engage in "baby talk" (speaking slowly, exaggerating vowels and raising the pitch of their voices) the sooner an infant will be able to produce his or her first words. Pygall agrees, adding that one-on-one engagement with an infant is crucial for language development.
"It's almost like watching an episode of The Wiggles and having to be that vivacious, exciting TV presenter, so your child is watching, engaged and thinking 'Wow, that's interesting', and they want to interact with that. It needs to be exciting so that it catches their interest," says Pygall.
A speech therapist will look at the whole picture, consider the child's listening and interaction, and may even make a house call to better understand the home environment.
They will then usually offer advice about changes that could be made to the environment, or opportunities that could be offered to the child. The opportunities might be as simple as suggesting that the child put on their own shoes if they are usually put on for them.
"Sometimes life is very busy, especially when you are in a household with more than one child. So it's a good idea to refocus. This provides parents with an opportunity to slow down, and look at what they [the children] are doing, and how they are doing it.
"This is particularly true when you are talking about a child who is not child number one," says Pygall.
For parents, that means being prepared to accept that their child needs help. This is not always easy, especially in Asian families, says Mr Lai, a father. Lai's son was nearly two when he became concerned that he wasn't talking.
"We are very Asian, and it's hard to deal with issues like that. Generally, we Asians prefer to deny it than confront it," he says.
But Lai and his wife did not shy away from the problem. They took their son to a paediatric psychologist, who said that, although he seemed to have some autistic traits, it was too early to tell, and he may grow out of it. Lai then consulted a speech therapist and an occupational therapist.
"It's not as simple as sending the child to a classroom with a therapist. The experts do an assessment and put down the foundations, but most of the work needs to be done at home, with guidance from the parents," says Lai who gave up his corporate career to be a stay-at-home dad.
The situation brought a lot of psychological and financial stress, although Lai says that he was fortunate in that they were able to afford therapy. The fact that both children mentioned here are boys is no surprise. Pygall says only one in 10 children who experience speech development delay are girls.
"But if a girl does have a speech and language disorder, it tends to be more severe than in boys. So we think it's a genetic indicator," says Pygall.
It's sometimes necessary to be concerned about the children who are speaking. If they are talking a lot, and the topics don't link, the content isn't relevant, or the reply doesn't answer a question that has been asked, then it could be that the child is not able to understand language at the level he is using it.
A number of educational aids and classes promote language development, but Pygall warns that not all are suitable.
Pygall points to the drive for children to adopt Putonghua as a second language, something which has children as young as one being sent to lessons.
"Some classes focus on phonics, or learning to count, which are prerequisites for primary school. But these need to be taught in a functional way, rather than as rote learning.
"All the research says that if you're able to learn a language, then you're able to learn a second language. But if you're having difficulties learning one language, then you will have difficulties learning two," says Pygall.