Table 3 reports difference in means and
medians of audit fees classified by types of auditor’s
opinion. The results in Table 3 panel A shows that
firms with modified opinion have higher audit fees
than those with unqualified opinion and this
difference is significant at 1 percent level. This result
supports the first hypothesis (H1). The results in
panel B describe types of modified opinion (i.e.
unqualified with explanation, qualified and disclaimer
of opinion) and compare them with unqualified
opinion using analysis of variance (ANOVA). There is
no classification for adverse of opinion due to two
reasons. First, adverse of opinion represents
disagreement between auditors and management in
accounting policy application and/or disclosure that
has a very material effect to financial statement. This
case is rare in Thailand. The second reason for
adverse of opinion comes from limitation of audit
scope incurred by circumstances and clients’
management so this type of report is unacceptable
by the SEC. The results present that means and
medians of audit fees for firms with unqualified
auditor’s report are lower than those with unqualified
auditor’s report with explanation and qualified
auditor’s report. However, firmswith disclaimer of
auditor’s opinion show the lowest audit fees among
other classifications. The result shows that there are
significant differences among audit fees in each
types of auditor’s opinion; however, it does not
report which types of opinion have influenced the
results. Thus, further investigationis performed in
Table 4 in order to magnify the results and indicate
which pairs of opinion have significant difference.