In addition, we find out that people tend to use the language that is the most commonly used in their social circle.
Since the Thai-Chinese would like to fulfill the purpose of communication, they will use Cantonese if they are talking to their friends in Hong Kong. It may not be an intentional convergence (Giles & Coupland, 1991) that they would like to show that they are part of the community, but rather a more natural and direct language choice.
Giles, H., Coupland, N., & Coupland, I. U. S. T. I. N. E. (1991). 1. Accommodation theory: Communication, context, and. Contexts of accommodation: Developments in applied sociolinguistics, 1.