As TW and I have been an item now for 7 years I have recently drawn up and had duly witnessed two new Wills which are cross reference to each other. The Thai Will basically enables TW to get into my Thai bank account, she has everything else in her name including our car and properties etc. Without checking and IMO Immigration would not accept a joint named bank account with funds for my visa extensions.

Question:- Does this Thai related Will have to be translated to Thai and resigned to be legal document here or is it acceptable as is, written in English this being my native language?

Can't answer the will question but joint account (with wife) was always acceptable for Thai wife extension and believe most officials will also accept for retirement if deposits are foreign sourced but would check your office before making the change.