If only 1 parent can attend then your wife needs to get a Kor ror 14 from the local Ampur. There are several reasons they can issue the form and you not being in the country would be one of them.
Then 1 parent takes the child along to the passport office with their old passport, ID card, blue housebook and the Kor ror 14 form.
My wife has just done this and renewed daughter’s passport in Phuket. They will only issue a 5 year passport and not the new 10 year passport as she is not an adult.