If you return to Thailand with a reentry permit a TM30 is not required unless you are changing address.
Which immigration office?
OP your wife needs to do TM30 for your guests since they intend to apply for an extension. Do not concern yourself that it wasn't done as soon as they moved in.
Do it prior to them applying for extension.
2.2 in this.....
https://aseannow.com/applications/core/interface/file/attachment.php?id=689134