Hi Below FYI is my experience of being an Executor for a Thai Will - my circumstances are not the same as yours but I hope the information will be useful.
My Thai Wife passed on last September and I was the Joint Executor of her Thai Will. I appointed a Lawyer in Chiang Mai to collect the paperwork, submit this to the Courts and obtain the Court Order to confirm I was one of the Executors. This took just under 3 months to complete and required me to attend a Court Hearing and answer the Courts questions under oath. Because of covid the Court asked that this be done via Zoom with me in my Lawyers Office. The Hearing was all in Thai and the Court wanted to satisfy themselves I was a suitable person to carry out the Executors duties. My Lawyer charged me Bt20k for this service, I found him to be honest, efficient and a reasonable fee, but he only speaks Thai - happy to share contact information if of use.
Armed with Death Certificate, Court Order, proof of my ID and Wife's ID I closed several Bank Accounts she had opened. All the banks required the 2 Executors to be present in the Branch when closing the accounts, though the process was different in each bank. With the except of an Agricultural Bank they did not require me to go to the branch where the account was based, i.e. I could do the paperwork etc at any of their branches. Most banks required me to open an account in my name for receiving the balance of my wife's account. The process varied from being all done in 1 hour to taking up to 2 weeks.
Hope this is of help