While information is available on the official Thai Embassy website for your country it may not be fully up to date (UK one is not iirc.)
Also be aware that some rules change rapidly and what worked a month ago may not now.
All out of country applications are now made through e-visa online.
Apply for the 90 day retirement entry
Iirc:If capital qualified, proof of funds (b800k or equivalent) must be in your sole name, not a joint account.
If b65k monthly pension qualified, you need certifcation of 'pension' source. ( I shall not cover this method as I am not familar with it.)
Health insurance must cover 1 year.
As soon as you get to Thailand your first priority should be to get a Thai bank account as this may be the most difficult aspect. (An 'introduction' from a respected local bank customer may help)
When relevant funds are transfered into your Thai bank account it needs to be shown as foreign exchange transaction (FET) or it may be questioned later.
Those funds then need to 'mature' untouched for at least 30 days before you can apply to have an extension of the 90 day visa for an additional 12 months (the earliest you can apply for the extension varies regionally so check).
You will then need to present further proof the bank funds have not gone below b800k at 3 months after the application for extension, and maybe sooner too.
Do NOT let the funds shown in the account drop below b800k for even 1 day in the first 3 months.
Month 4-8 the funds can drop to b400k but must go back to b800k at month 9 to apply for renewal.
If you arrive on a 60 day visa waiver or other 'tourist' visa you are likely to find it very difficult to open a Thai bank account which you will need to apply for a change of visa. Reportedly even agents are finding it difficult now. It does vary from bank to bank and region to region.
Without a Thai bank account you will not be able to apply to change to a retirement visa.
As I mentioned earlier I am not familiar with the b65k monthly pension procedures but do know that in country applications require certification through the embassy of your country and this is not available to UK or US passport holders.
All the above is based on my recent experiences but the rules and implementation do seem to change rapidily and regionally.
Almost, the b65,000 has to come from a recognised certified 'pension' source (but US & UK Embassies no longer give certification) and that b65,000 must be deposited each and every month of the visa's validity or the visa becomes invalid, and you have problems (like rejection) on renewal.
30 minutes car ride (with 'vibrations) is about 10km at worst.
Many options are available if you consider.
Walk: at worst 3 hours, maybe longer depending how long you stop at cofffe shops en route to rest.
Bicycle: at worst 2 hours, though the biggest problem might be balancing upright if riding that slowly; alternatively a tricycle so you can sit down while resting.
Ambulance: you can hire a private ambulance to carry you to and from immigration office. They are specifically equipped with air ride suspension to absolutely minimise any vibration, added benefit medical assistance on hand should you need it.
VIP taxi: With a good driver you may not even notice you are moving.
Or use an agent that offers a servicecyou can cope with.
Alternatively if you can create a medical treatment plan to mitigate or alliviate your symptoms a medical DTV might work for you.
Lastly, give your head an 'attitude adjustment ' wobble.
Your choice to use a bus, which is very likely to have vibrations, that exacerbated a pre existing condition, has led to your current situation.
No reason not to comply with the reasonable requirements of Thai immigration.