However, there are two forms
of validity in case study research: internal and external validity (Golafshani 2003; Rubin
& Babbie 2005). In internal validity, five clusters of Thai SMEs were introduced by the
Thai Ministry of Industry and seventeen cases were analysed. According to the data
collection process, semi-structured interviews were used as they allowed the
interviewees to be free to introduce issues that they considered relevant for discussion.
To ensure that internal validity exists, the researchers have to be able to answer whether
findings or conclusions correctly map the experience and that whether the substance of
the data is relevant in the study.