The process for adding a comment to a TON-related transaction using send_raw_message involves appending the comment in hexadecimal format to the end of the message body.

This can be achieved by adding "0x00000000 + comment_in_hex" as the last line of the message body.

Alternatively, it is possible to remove the "store_slice(msg_body)" command and store the comment directly using ".store_uint(0, 32)" followed by ".store_slice(comment)". This will produce the same outgoing message with a different code.

Overall, adding a comment to a TON-related transaction using send_raw_message involves modifying the message body to include the comment in hexadecimal format. It is also possible to store the comment directly, but the code will differ from the standard approach.