The question marks which you see instead of correct characters is due to an issue with the control-based version of the F4-Help. It only works correctly with a Windows locale (Regional Settings) which corresponds to the current SAP system Character set. It means you need to set your Windows Regional Settings to Thai or use the dialog-based version of the
F4-Help instead. To change your F4 Help Settings, please go to: Help -> Settings -> F4 Help -> Dialog
Please also refer to Attachment 'I18N_Guide.zip' which is attached to Note: 508854, section 1.7.