Any vaccination you have had bring any proof you can like a certificate that will help you and don’t forget you need to fill out a Location form before you fly back to the UK
For example, if you were initially supposed to fly into Thailand on Jan. 1st at 1pm, you would be permitted to enter any day / anytime before 11:59 pm on Jan. 4th?
Normal UK travel insurance will cover you for the $50,000 cover that Thailand requires you to have I personally used Sainsbury’s travel insurance when I applied for my Thailand Pass (TP) a few months ago