Custom certificate (plugin)

Hi Chardelle,
I tried to set the course name in Thai language. Inside of Moodle is displayed correctly.

การปฏิบัติตามกฎระเบียบ ภาษาไทย
(Compliance Training)

But even when I use the Unicode versions of the certificate (Unicode portrait) I only get question marks shown instead of Thai letters.

Whats wrong?

Charly