Ill try again. There are two families both move to Bangkok for education of the children and parents as dependent, both families have the same nationality.

Family 1 enters on August 3 with a 90 days visa (Ed and non immigrant O) and get stay until Nov 1. In mid October they get extension of stay and get a stamp until 30/06/19 so total 11 months they all get exactly the same parents and children.

Family 2 enters on August 20 with a 90 days visa (Ed and non immigrant O) and gets stay until Nov 18 today they get extension of stay and get a stamp until 30/10/19 so total 14 months and 10 days they all get the same parents and children

My question is given the exact same situation why this difference ?