Numerous studies have been conducted to ascertain the relationship between the first language (L1) and the second/foreign language (L2). However, it is unclear how vowels and consonants affect how a foreign language speaker pronounces Indonesian. Thus, the objective of this study was to ascertain the vowels and consonants of the Indonesian language that were incorrectly and correctly pronounced by Lao men and Japanese women. This study is descriptive qualitative in nature. Following data collection via audio recording, the collected data were analysed using a contrastive analysis. The study's findings indicate that certain speech sounds are both mispronounced and well-pronounced. The speech sounds /i/, /u/, /e/, /ə/, /a/, /p/, /b/, /m/, /d/, /n/, /r/, /l/, /t/, /h/, and /k/ were mispronounced by the Japanese participants; however, the speech sounds /i/, /u/, /ə/, /a/, /ʤ/, /n/, /t/, /g/, /p/, /k/, /r/, and /h/ were not pronounced correctly by the Lao participants.