In general, not only does a writing teacher provide feedback according to the errors he/she has seen in students’
written work, but also a grammar lesson based on the errors found can be more effectively prepared in
accordance with a writing genre being taught. As seen in Figure 2, the L1 error categories of narrative,
descriptive, and comparison/contrast writing genres are compared and presented. This indicates that, in narrative
writing, an intensive focus of errors should be on verb tense, while subject-verb agreement should be the focus
of descriptive and comparison/contrast writing. Overall, among these three genres, word choice, sentence
structure, preposition, verb form, run-on sentence, modal/auxiliary, and transition are seen to occur
comparatively equally. In description, the uses of article and word choice become the first two error types that
should be taught to L2 student writers. It may be because of the topic assigned to the participants to write as they
were required to use a lot of nouns and adjectives in order to describe their ideal houses. Since the Thai language
has few or no articles or determiners in front of nouns, this error category emerges as a frequent writing problem
for Thai students. In terms of comparison/contrast writing, comparison structure errors arise the most, compared
to the other two genres. Therefore, it is necessary to emphasize this structural feature when teaching L2 students
to write comparison/contrast paragraphs.