I am confused as to what type of health insurance is required to obtain a visa. The London Embassy website onlyrefers to COVID insurance and not a General Health Insurance policy. Is this correct? Their website does seemas if it requires updating!

A TV will allow you to stay 90-days (30 day extension on top of 60 day permission to stay on entry). Tourist visa does not require any health insurance. (only TP requires Health insurance). Of course it's prudent to buy a travel insurance for 90-day (not legally required) for one's peace of mind. 

Edited May 23, 20224 yr by CartagenaWarlock

There are insurance companies listed in the Thailand Pass information ( 3 companies I believe)

One at least (the most expensive naturally) I believe offers other insurance cover with their Covid cover.

 

https://direct.axa.co.th/TA-Inbound/CoverageOptionPlan/Agent/9F89526D81

IF you need 90 days of stay here then apply for a single entry tourist visa from the thai consulate in the country you're in before you wing your way here

As people pointed out that visa type does not require any health insurance to purchase, you will get stamped in for 60 days when you arrive and you can extend that ONE time for 1900baht at the immigration office where you stay once you're here

You WILL need to have the 10K USD mandatory health insurance (for at least 30 days) to get your thai pass approved but that has nothing to do with the tourist visa, 
here's where you apply for the tourist visa (via the eVisa web-link)
https://www.thaievisa.go.th/

here's where you apply for the thai pass
https://tp.consular.go.th/

How long do you plan on staying in Thailand?

Other than applying for a tourist visa you have the option to enter the country visa exempt that will allow a stay of 30 days that can be extended for 30 days at a immigration office.

You would need a ticket out within 30 days if it the airline ask for one to check in for your flight to here. It can be a one way ticket to anywhere or a temporary onward ticket that can obtained from many sites online.

The OP requires 90 day visit.

 

His best option is outlined above by @Tod Daniels

 

If SETV was not available or he wanted to avoid obtaining one then visa exempt + extension+ border run is an option, however very messy at this time. 

They didn’t check me for an onward ticket for 30 days and my flight returned in 60 days. So it’s the luck of the draw. 

2 hours ago, jcmj said:

They didn’t check me for an onward ticket for 30 days and my flight returned in 60 days. So it’s the luck of the draw. 

Which airline and route?

Many reports from folk stating exactly same experience as you related. 

Problem is also Many experiences of onward flight being required.

I don't like travel that relies on "luck of the draw".

We often read suggestion of throw away ticket and "rent a ticket" from the onward flight sites in case flight is required. 

 

Another option is to roll the dice and be prepared to step away from check in (if refused) and buy an on the spot throw away ticket.

Obviously you would require internet access. 

I’ve done it on JAL and Qatar. Both times no issues I had an agent question my return ticket once but told them I was getting a 30 day extension like before. Showed her it and was no problem. Maybe I was lucky. Now I’m getting my retirement visa so hopefully no more issues with that.