Vocabulary in Thai Textbooks: A Corpus-based Study

Abstract

This study analyzed vocabulary in Thai textbooks used for teaching children ranging from preschool to the twelfth grade, which was categorized into four levels of education. The hypotheses of this study were 1) the vocabulary of textbooks in the higher levels subsumed vocabulary in the lower levels; 2) the number of three-syllable words and opaque words in higher levels were higher than those in the lower levels; and 3) the same verb found in the higher levels had more meanings and usages than those in the lower levels. According to the list of vocabulary taken from three-million-word Thai Textbook Corpus, it was found that the vocabulary in the higher levels did not include every word in the lower levels. In terms of word difficulty, the findings revealed that the number of three-syllable words, and the opaque words tended to increase in the higher levels. As a result, these factors could be used to indicate the difficulty of vocabulary. However, in the case of high frequency words with multiple meanings like the verbs ‘go’ (/paj/) and ‘come’ (/maa/), it was found that there was no increment of meanings according to the levels of education since all of the meanings of both words were already used at the first level. Besides, the findings indicated that the vocabulary in level 2 (4^th-6^th grade) had the widest range of vocabulary, which contributed to the increasing number of vocabulary of learners more than other levels did.