What are the steps and requirements for switching from a Non-B Visa to a Retirement Visa in Thailand?

Good morning- I think my plan to change from working on WP and Multi Entry Non B Visa to Retirement VISA is clear but T.I.T so I don’t want any surprises - review and approval of my plan and questions please 🙏

I am 51 and have been in Thailand 3 years- my employment finishes on June 30th.

I have had more than 800K in the bank for 2 years and will get a letter from the bank to confirm. Will also take my bank book and copies for the same account.

I have downloaded and completed form TM-7.

I have the 1900 THB.

I have the passport, copies and the photos.

I have copies of my lease contract (not sure if I need this)

Questions:

Do I need to take a medical certificate?

Which Bangkok office does the retirement visa ? ( I live on Petchaburi Road/ Asoke)

Do I need to wait until my employment finishes on June 30th - or can I go on Monday and take and use the letter from my employer that confirms the termination date ?

I am approximately 30 days into the current 90 day reporting period.... my current visa is until Dec 20 ( but I read something about having to be in the last 30 days of my current extension.... I am not, but my employment ending would trigger cancellation of my as my employer tells me that ‘by law’ they have to submit and cancel both visa and wp within 7 days of employment ending.

I want my retirement extension to be ‘multiple entry’ - do I just ask for that and pay more - how does that work ?

Any advice and clarity greatly appreciated...