Hi Khun June,
Earlier I had used TIS-620 encoding in PI interface and it was working end to end perfectly while testing with Khun X.
This week, I had changed to UTF-8 because it was not working for TIS-620. I am not sure what has been changed at system level since then.
May I ask, what kind of encoding, your team have been using while transferring the file to TCC techno and ISIS. Can you please try with UTF-8 once, if not tried yet.