Jitrlada RojratanavijitPreecha VichitthamarosSukanya PhongsuphapMahidol UniversityThailand National Institute of Development Administration2019-08-282019-08-282018-01-01Walailak Journal of Science and Technology. Vol.15, No.1 (2018), 63-802228835X168639332-s2.0-85037108904https://repository.li.mahidol.ac.th/handle/20.500.14594/47540© 2018, Walailak University. All rights reserved. The emergence of Twitter in Thailand has given millions of users a platform to express and share their opinions about products and services, among other subjects, and so Twitter is considered to be a rich source of information for companies to understand their customers by extracting and analyzing sentiment from Tweets. This offers companies a fast and effective way to monitor public opinions on their brands, products, services, etc. However, sentiment analysis performed on Thai Tweets has challenges brought about by language-related issues, such as the difference in writing systems between Thai and English, short-length messages, slang words, and word usage variation. This research paper focuses on Tweet classification and on solving data sparsity issues. We propose a mixed method of supervised learning techniques and lexicon-based techniques to filter Thai opinions and to then classify them into positive, negative, or neutral sentiments. The proposed method includes a number of pre-processing steps before the text is fed to the classifier. Experimental results showed that the proposed method overcame previous limitations from other studies and was very effective in most cases. The average accuracy was 84.80 %, with 82.42 % precision, 83.88 % recall, and 82.97 % F-measure.Mahidol UniversityMultidisciplinaryArticleSCOPUS