Khmer language words sorting

[yazwas]

Good day

I'm trying to sort a list of Khmer words, but so far I'm not successful. I'm using UTF-8 and qSort to do the job, but there is something wrong, or something missing.
(the below code worked ok for English and French)

bool caseInsensitiveLessThan(const QString &s1, const QString &s2)
{
    return s1.trimmed().toLower() < s2.trimmed().toLower();
}
 
void mySort(QStringList &list)
{
    qDebug() << "unsorted list: " << list;
    qSort(list.begin(), list.end(), caseInsensitiveLessThan);
    qDebug() << "  sorted list: " << list;
}

bool caseInsensitiveLessThan(const QString &s1, const QString &s2)
{
    return s1.trimmed().toLower() < s2.trimmed().toLower();
}

void mySort(QStringList &list)
{
    qDebug() << "unsorted list: " << list;
    qSort(list.begin(), list.end(), caseInsensitiveLessThan);
    qDebug() << "  sorted list: " << list;
}

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This is an example list I have that is sorted, and should not be resorted when using the sort code.

ក1, ក៏2, កក3, កក់4, កករ5, កកាត6, កកាយ7, កកិចកកុá� �…8, កកិត9, កកិល10

but when using my sorting code (above), I'm getting this list.

ក1, កក3, កករ5, កកាត6, កកាយ7, កកិចកកុá� �…8, កកិត9, កកិល10, កក់4, ក៏2

Any suggestions are most welcomed?

Thank you