Comment 3 for bug 301696

Yes, this is a known problem(see https://bugs.kde.org/show_bug.cgi?id=174110 ), and not an easily solvable one unfortunately.
You can use the same workaround I explained in the kde bug report, change the layout using the setxkbmap command, like for german keyboard:
setxkbmap de

For thai, replaces "de" with "th", etc using the layout name. It's shown by the systemsettings keyboard layout module next to the country name.