Have an appointment at Chiang Mai immigration next month for one year visa renewal but really don't want to bring a seven month old baby and my wife, didn't have this problem last year.

Does anyone know can I just bring their passports and paperwork or will the authorities make them come also. Thanks

If it is to apply for an extension based on marriage you will need to take her.

No, we are both non-Thai, just standard Non-O renewal.

Is your wife piggy backing your visa?

It depends on the reason for which the application for extension is made.

If you are asking if your wife and child also have to go to immigration for their application for an extension of stay, the answer is yes it is officially required they show up in person. But that is not always demanded.

The baby will not be required, if born inThailand (s)he doesn't need a permission to stay till (s)he has left Thailand and return. Upon return a visa woud be required.

As said application needs to be made in person. Although believe exceptions can be made believe arrangement should have been made in person and in advance. As said child would not have to attend. As Chiang Mai uses an appointment system do not believe visit would have to be very long.