What documents are required to extend my STV visa in Thailand before the September 30th deadline?

The user is currently in Thailand on an STV visa and is seeking information on the documents required for extending the visa, noting difficulty in finding this information online. They also express concern about the end date of the program, September 30th, and whether they can extend the visa before or after this date since they are already in the country. A comment suggests checking the local immigration office for the latest requirements and indicates that September 30th is potentially the last day to apply for an extension, urging the user to stay updated on any changes.