Comment 10 for bug 539008

This does help to solve the problem described (add it to a new global system wide fonts conf file or to a custom user only place as described by fontconfig docs) - but having the thai package still there.

<match target="pattern">
                <test qual="any" name="family" compare="eq">
                        <string>MS Sans Serif</string>
                        <string>Microsoft Sans Serif</string>
                </test>
                <edit name="family" mode="append" binding="same">
                        <string>DejaVu Sans</string>
                </edit>
</match>