The last factor is the motivation from their identity.
Some of them regard the ability to speak the Thai language as a characteristic of a Thai-Chinese. This motivates them to learn more about the Thai language and the culture. For example, one of our interviewees minors in the Thai language at the University because she would like to learn more about this language. On the other hand, the younger brother of the third family has less motivation to acquire the Thai language as he believes that he is a Hong Kong-er so it is fine for him just to know Cantonese and English, which are the dominant languages in Hong Kong.