The purpose of this study is to study an English loanwords or lexical borrowing found in the advertisements in four Thai magazines. The analysis was divided into two parts: types of loanwords and semantic changes. There are four main types of loanwords: transliteration, loan translation, loan blend, and loan shift; and the second part is related to four main kinds of loanwords according to semantic changes: original, narrower, broader, and deviating meaning loanword. The data were analyzed according to the method of assimilation into English and Thai context. It was found that transliteration was used most in each magazine. Moreover, original meaning was used most in the contexts according to semantic changes. In conclusion, this study offers insight into English loanwords in the Thai language with a special discussion on the effects of the loanwords on writing in the advertisements.