What are the options for renewing a family member's tourist visa expiring on December 31st, and is immigration open on that day?

The user seeks information on renewing a family member's tourist visa that expires on December 31st. They inquire about extension options, specifically if the renewals are processed at the Chaengwattana office, and if immigration services are available on December 31st. They also want to clarify if the extension will begin on the renewal date or the original visa expiration date.