You can go to Thailand as a tourist have one of the little shops help you convert to a retirement visa. There is a slight advantage to having your visa issued in Thailand rather than overseas as there are less health insurance requirements. But that could change at any time. Just getting to Thailand is a long convoluted process right now anyway.
To be clear, the 25K for retirement visa you get to keep your money, and can actually draw down from that account throughout the year as long as you top it up again when it comes time for your annual renewal. Many people choose to leave the Baht 800k balance steady in their account to avoid complications.
As opposed to the Elite visa where the approximately equivalent fee as ndt mentions is the cost of the visa itself. But there is no minimum age requirement.
Personally, if I was coming and going frequently in and out of Thailand and had a good income I might opt for the elite visa; but if I was over 50 and planning on staying put the retirement visa works well. For now.