What are the rules for extending a Non-Immigrant O visa for guardianship in Thailand?

Clarification for extension of stay for non immigrant O visa based on guardian for children education all expats in Bangkok. When I went to do mine I was clearly told that the bank book showing the 500,000 had to be updated to the date of the application and that the month was calculated starting from then. Have a friend who will be doing the same and was wondering if what happened to

me is a rule or just the immigration officer I had, since if it is the case it eliminates the possibility of going in early. Any help would be appreciated.