Every immigration office has its specific requirements. Whenever a new boss takes over an immigration office, he/she will implement a few small changes to leave his/her mark. Hence changing requirements in each office over the years.
When you ask your bank to transfer money overseas (out of Thailand) they will ask you for a reason. If you give a credible answer they will proceed with the transfer without conditions.
you can purchase a re-entry permit either at an immigration office in town or at the immigration counter of an international airport before leaving Thailand. You will need the TM8 form, copy of passport (main page and visa) and a 4x6 photo.
You do not need any insurance or paperwork to re-enter Thailand, other than your passport and a Covid vaccination certificate. If you are not vaccinated you will need a negative test result.
Note that the permit to stay extension and the re-entry permit are 2 separate permits. Both will still be valid in October so you are ok. But your re-entry permit is a permit for a single entry. If you leave Thailand for a second time and intend to re-enter you will have to apply for a new re-entry permit. You can apply for a single, or a more expensive multiple one, depending on your travelling plans.