You can only be careful in your choice, firstly using broad indicators as I gave, then looking at fine detail, perhaps especially around dangerous sports. People routinely bungee jump, but it is mostly categorised as a dangerous sport. Mountaineering and rock climbing can be an outright No or dependent on exactly what is planned and using what equipment. All this said, which should be obvious, people do as the insurance companies do and look at heart risk with age, stroke risk with age, etc and try to see a relationship with health to date. Certainly that has some truth. But consider the very high rates of death and injury in Thailand in motor vehicle accidents, including as a pedestrian. Sure it could be that responsiveness reduces with age, but truth is that insurance companies tend to take those on the nose, although a hugely important category. On the road accident an important point is do you think that the rudimentary emergency services here will pick you up without an insurance card. Ditto the hospital take you in (legally they have to but that is often not understood. Cough!!!!! - its Amazing Thailand, including such amazing language misunderstandings!). So you carry around a credit card and can genuinely access large amounts that way (and they need to be large). Now how is the risk management looking? Or do you want to be left in the road - it can and sometimes does happen: the care obligation at law, as best I understand, only laying with the hospital.
The starting point is your country of residence. The relevance is what insurers have products available to you. You appear to be UK based, so that becomes the point of reference, for instance Japanese insurers tend to be the good guys. Whether available in UK I don't know. Things changed with COVID, many companies withdrawing from their peripheral markets. US tend to be the ones best avoided. They tend to be at the forefront of avoiding payment of claims, wriggling out however they can. British companies tend to the in-between position and likewise on price (You pay for Japanese reliability). Be very wary of cheap cover and always, always consider a company's registration and legal jurisdiction. The financial authority of, say, St Kitts might not be the best backup beyond the company. Above all, whoever the insurance provider, your own behaviour is a key. On a motorbike with no helmet - what do you expect the insurer to do? More or less the same for on a motorbike at all. Don't listen to bike hirers saying it's OK. Or even saying you are insured. This is Thailand. Dangerous sports, definitely no cover -and you'll be surprised what constitute dangerous sports. You need to make yourself very, very aware of the small print. And be aware of the pretty lawless milieu here. Don't trust smiles - and that isn't just a reference to Thais but also farangs. Free meals are very few and far between in this life and that includes Thailand as much as anywhere!
Truthfully it is impossible to say without knowing names and quotes. Are we talking Blue Elephant or Dusit Thani or Dao's Disastrous Dishes. To be honest the location doesn't sound promising unless Dao charges low and sorts the visa issues.
Wow! Clear advice is simply unavailable for the way so many people actually work. This becomes a great indication of the art of the possible, hugely valuable - but, of course, what happened in Phnom Penh isn't necessarily an indication for elsewhere, the usual problem of Thai officialdom.
I take your point but it is a discussion best not begun or we will move toward looking at educational standards among arriving expats. I mean formal education there. But you could argue that as irrelevant and the thing to focus on is "street" navigational skills, but those have collapsed too.
Good to have up to date and specific information. What happened even a few years back can be of no relevance. I have certainly never paid to open an account, but most of my accounts were set up years back. That said one was set up in 2022 and no issues. But on all occasions all my ducks were in a row and no stupidities like tourist visas, etc. Something was interesting about 2022, simply that the bank was a very unusual choice. Why do people keep going to banks that we have heard of over and over again refusing? Yes, different officers, different days is an argument, just as with Immigration, but constant rejection is a fair indication so why try bank X?
How long ago? Things have changed very rapidly of late, including some new banking rules coming into play. Agents are the way now, no matter how much shoe leather you are willing to put into saving say 3,500 -5,000. Maybe 8-10K in Bangkok.
On the address. Agents have relationships where they have relationships. You change the address subsequently in TM30 registration, then follow that through on your TM47s (90-Day Reporting). Finding an agent to get a bank account for you locally may be more difficult but important as you don't want to find yourself paying out province bank charges often and change of account province isn't regularised in the way the Immigration procedures just described are.