No you can't.
You need to wait until you reach the state pension age, which is currently moving further and further into the future
The visa, or extension of stay based on retirement that is available in Thailand requires an income of ฿65,000 per month, or a lump sum of ฿800,000 which has been in a Thai bank account in your name, for two months prior to the first (yearly) application, and three months for the following years.
Given that the current single person's state pension is around the £100 a week mark, that would be somewhere just shy of ฿25,000 per month. Not enough, and you can't have it when you're 50.
I know you're trying to think of all the ways that you can go and live in Thailand, as you've just got back from an amazing holiday, but you really need to think it all through and have a solid plan.