Interviewing is the most frequently used technique for collecting data, but it has its share of methodological problems. Thailand has few studies on methodology regarding the effect of interviewer characteristics on the data quality, and so there is little empirical research on methodology development or recommended changes for improving the existing method of social survey. The three objectives of this study are 1) to assess the quality of survey data regarding item non-response, accuracy and response reliability, 2) to investigate the effect of interviewer and respondent characteristics and social environmental attributes on the quality of survey data, and 3) to investigate what are the determinants affecting data quality as regrads the efficiency and effectiveness for contact strategy. This study focuses on data collection of the Kanchanaburi Project of the Institute for Population and Social Research Mahidol University with support from the Welcome Trust of the United Kingdom. I used multilevel analysis and structural equation (path analysis). I found that the interviewer being of a different gender than the respondent or a third person presence at the interview adversely affected all three categories – item non-response, accuracy, and response reliability. Other factors adversely affecting one or more data quality indicators included: interviewer speaking a different native language than respondent or having less interview experience, interview being held in the morning, and respondent being younger or of lower education. Ultimately, this study serves to show that characteristics of interviewers and respondents and some social environmental factors affect the quality of survey data. Results of this study would be used in setting up guidelines for interviewing to account for the interviewer’s potential effect on the process, for example the effect of difference of gender, language, etc. These serious problems may affect the objectivity of research. A survey should start with a well thought out study design that includes a method to monitor the quality of the survey.