This study aims to identify the linguistic characteristics of Thai-English code-mixing on Instagram by Thai users using qualitative research data collected from the captions and comments of 40 Thai users on the Instagram social media platform. To examine the linguistic characteristics, a linguistic analysis was applied. The study has discovered five distinct linguistic characteristics of Thai and English code-mixing; (1) lexical insertion, (2) word translation, (3) word repetition, (4) specialized features, and (5) switching to the Net culture. In addition, Thai and English code-mixing is used to express emotions and feelings while revealing Thai social and bilingual identities. Overall, this study makes a contribution to the rapidly growing area of computer-mediated discourse analysis with implications for better understanding of language exchange in online community, bilingualism and innovative research methods in applied linguistics.