in reply to Re^7: Listing out the characters included in a character class [naming mismatch]
in thread Listing out the characters included in a character class

If they really want to load package Regexp::CharClasses::Thai from a file Regexp-CharClasses-Thai.pm, then the following should work:

BEGIN { require 'Regexp-CharClasses-Thai.pm'; # resp. ideally use the full + path Regexp::CharClasses::Thai->import('IsThaiDigit'); }

(see also use)