Many language scholars such as Kurk and Atay (2007) and Latif (2007) addressed that the most difficult task of EFL students is to write in English especially use of prepositions. Hence, the study aimed to investigate the misuse of prepositions and to identify interferences of first language (L1) features appearing in written productions of Thai EFL learners. Twenty participants were first-year Srinakharinwirot university majoring in Education (English). One hundred twenty written works were collected and established as a corpus of Thai EFL learners’ written work. The concordance feature of the AntConc program was utilized to examine the errors of preposition use based on preposition errors classification by Burt, Dulay, and Krashen (1982). Moreover, some contrastive analysis techniques were applied to identify the interference of mother tongue toward participants’ preposition use on their written works. The findings were cross-checked by two EFL instructors and shown that there were misuse (100 times, 70.92%), addition (21 times, 14.89%) and omission (20 times, 14.18%) of prepositions found in the corpus. The most problematic English prepositions found in the corpus were ‘in’, ‘to’, ‘of’, ‘at’, ‘with’, ‘for’, ‘by’, ‘about’, ‘on’ and ‘from’, respectively. Furthermore, there were two mother tongue features that were semantic-related and syntactic-related L1 interference which interfered the preposition use of Thai EFL learners. Thus, it is an English language teachers’ responsibility to raise the awareness of the differences between mother tongue language and target language to Thai EFL learners during the writing lessons in order to overcome the problem of misuse of prepositions. Moreover, corpus program could be considered as one of the beneficial tools which assists Thai EFL students to reflect and learn from their written errors, as well as they could overcome their misuse of prepositions.
Keywords: L1 Transfer, Misuse of Prepositions, Corpus Study, Contrastive Analysis