I agree with my friends’ previous answers, and I can think of another confounding factor: living area and location. Since we don’t know the demographic characteristics of the study subjects in Thailand, the location setting could affect the relationship between age and contact patterns, leading to incorrect conclusions.
For instance, young adults may tend to live in urban areas with higher population densities. These areas typically house top colleges or universities, as well as workplaces that require frequent social interactions. Furthermore, urban areas often offer numerous social activities that are attractive to young adults, who tend to have more active social lives compared to other age groups. Due to the higher population density in urban areas, young adults may be more likely to use contact tracing applications and had the most active contact pattern than other age groups.