There have been numerous threads on this--likely some by you. Can you live on ________ amount in Thailand? Fill in various amounts, including the latest, yours, of 40k. If you have read any of those numerous past threads, you'll recall a lot of different answers. But, basically, it pretty much boils down to two. You have the posters who say, no way could they live on _______ amount. And, you have the posters who say they could easily live on _________ amount, with some posting that they could live on even less.
A responsible person will make whatever amount they are working with meet their needs. And, especially if that amount is small, they will do that by adjusting their needs according to the amount they have. When my spouse and I first moved to Thailand in 2010, our income dropped quite a bit and we were living on just a pension of around 65,000 baht a month, about what Immigration requires. I would turn 59 that year and Social Security would not kick in until I turned 62.
65,000 baht is not a lot, especially for two, but it's more than some receive and we made it work by making adjustments. That meant buying a small condo to save on rent. That meant buying a small condo we could afford and not a large house we couldn't afford--living within our means--which many have never learned to do. Could we live in a small, one-room studio with only one bathroom and not kill each other? Yes, we could--and we did. A studio was all that was within our means at that time, so we made it work.
That's really all there is to it, whatever your income--living within your means. Being realistic and making it work. There used to be a popular expression, years ago when I was growing up, "Keeping up with the Joneses". If you're not a Jones, don't try to keep up with them. Keep up with yourself, instead.
Just as an aside, by buying, not renting, we put to work for us the largest chunk of money we had each month to do anything with to better ourselves--our housing money to keep a roof over our heads. Instead of paying a landlord rent, we paid ourselves. We used what we would have spent on rent to fix up the condo we bought and then we sold it--at a profit. Then, rinsed and repeated.