I have confirmed this situation with BTMT.
BTMT has internal control in their plant for indirect material control.
BTMT don’t permit color or other material contact with material directly except indirect approval material.
In case of permanent marker, it isn’t registered or approved in BTMT indirect material control list.
Moreover, nobody can guarantee that permanent marker can be contamination in the process or not.
Hence, they would like to ask supplier don’t write down any information with permanent marker on the package.
For BTMT internal control, they would like to reject Thong Thai rubber if they still use permanent maker.
What BTMT should do in this case? Could you kindly suggest?
For your information, NR suppliers in BTMT plant don’t write down any information with permanent marker on the package except Thong Thai Rubber.