Absolutely. The Aussies who have taken the 5+5 year OX are loving it. Not one cent tied up in a Thai bank account, which is a huge plus, if you can earn 7-8% tax free keeping your money in Aus. But, yep, it's each to their own, and plenty of options available
I'm looking at from the point of view of Australians. However you try to spin it, the 800k IS most definitely tied up for as long as you stay in Thailand under that extension. You talk of "hefty" fees, the OX is $600 for five years, which works out at 2800 baht per annum, with no visits to immigration required for five years. That's pretty neat I think. The OA is $300, which works out at $150 per year (no visit to Immigration) or 3500 baht. If you think these fees are "hefty" I can understand why you would struggle with the 65k/month process. But as I said, the Sydney Consulate is arguably the most "laissez-faire" consulate in the world, so the OX is a total winner for Aussies
It's a good option for retired Australians, as Australia has a very lucrative superannuation set up, which once past 60 is tax free, and earnings are generally in the 7-8% p.a. region. To withdraw 800,000 baht equivalent to put into a Thai bank account earning 1% is financial lunacy. The additional interest earned by keeping any such lump sum in Australia comfortably pays for insurance requirements. The smart people get declined for insurance and use value of assets in lieu of the insurance. Of course, Australians can also avail themselves to the OX 5 year visa, which similarly does not require any money transfer to a Thai bank account. Others have the option to visit their home country every 18-24 months and pick up a new OA each time, again negating the need to transfer money to Thailand. Personally I transfer 85k to Thailand each month, as I'm genuinely retired and wish to enjoy my retirement years to the fullest. The 65k is never tied up, any excess monies can easily be transferred elsewhere for a multitude of purposes. The 800k is essentially locked down forever, or for as long as you stay in Thailand. I simply couldn't bolt down such a sum of money. But it's each to their own and there's many options open. My stance is directed more at money-savvy retired Aussies
To avoid the 800,000 "dead money" process, take the OA visa (where money stays in your home country), which effectively gives you two years with just one border bounce. Commence the 65k per month transfers at your leisure, and towards the end of your second year, leave the country, visit an embassy which sells the non-O (50+) visa, re-enter on this, and after the 90 days, you can extend on the basis of the 65k per month regime. Keep in mind the 65k per month is money you can spend immediately, whereas the 800k is tied up for as long as you remain in Thailand. Financially the 65k is the preferred method.