The Combining Class is used for normalisation of strings. Normalisation of strings is important for filenames in filesystems.
As far as I know, a Thai consonant (Lo, Other_Letter) can have several Nonspacing_Marks. This cluster of nonspacing marks can contain at most one top/bottom vowel and at most one tone/other mark. There is no syntactically meaning in the order of these nonspacing marks. So: All top/bottom vowels should have Combining Class 103, all tone/other marks have Combining Class 107. Is there a reason for having top vowels or other-marks with Combining Class 0, Not_Reordered? With the current choice of Combining Class both consonant + mark + top vowel and consonant + top vowel + mark are normalised, so that one can have two files with these (identically looking, but different) names, which is rather confusing. Here a list of all nonspacing marks in the Thai script: top vowels (Combining Class 0, Not_Reordered): ← this seems to be wrong; should be 103 THAI CHARACTER MAI HAN-AKAT ั THAI CHARACTER SARA I ิ THAI CHARACTER SARA II ี THAI CHARACTER SARA UE ึ THAI CHARACTER SARA UEE ื bottom vowels (Combining Class 103): THAI CHARACTER SARA U ุ THAI CHARACTER SARA UU ู tone-marks (Combining Class 107): THAI CHARACTER MAI EK ่ THAI CHARACTER MAI THO ้ THAI CHARACTER MAI TRI ๊ THAI CHARACTER MAI CHATTAWA ๋ other-marks (Combining Class 0, Not_Reordered): ← this seems to be wrong, should be 107 THAI CHARACTER MAITAIKHU ็ THAI CHARACTER THANTHAKHAT ์ THAI CHARACTER NIKHAHIT ํ THAI CHARACTER YAMAKKAN ๎ other-marks (Combining Class 9, Virama) THAI CHARACTER PHINTHU ฺ Gerriet.
