How can we apply for Guardian visas in Thailand while resetting our tourist visas?

Hello, we are new to Chiang Mai, have been here for 9 weeks. I’m here with my husband and two kids, our kids are enrolled in an international school and will be getting ED visas soon. Through that, my husband and I can attain Guardian visas for the school year. We are unfamiliar with the process of applying for Guardian visas and will need to leave Thailand soon to reset our tourist visas while we are in the process of applying for them. My kids have appointment on November 3rd to change their tourist visas over to ED visas. At that point, we assume we can start the Guardian visas process. We were also told we would each need to have 486,000 baht each in a Thai bank account. We were also told we may need to have our kids’ birth certificates notarized, which we don’t have the original copies here with us so would not be able to do. Could anyone recommend a good Thai Bank and any advice regarding the original birth certificates? Could my husband and I leave every 2-3 months to reset our tourist visas? Is that an option for staying here long term?