L1 interference categories in each
text type should be considered as the first step of the development of teaching aids and course syllabi. That is, a
writing teacher has to prioritize what kinds of errors, especially in each different genre, should be initially
focused on, which a great deal of research, conducted in Thailand as well as in EFL/ESL contexts, failed to
mention. According to the results of this study, it can be seen that each writing genre had different numbers of
error frequency, which could be used to strongly claim that when teaching writing, a genre also had an impact on
L1 error categories. To clearly explain, a comparison of error types found in three genres is shown in Figure 2.