Summon the devil, and beware what might appear, Khaki!
My Merida experiment was in 2014. (Wow, how time flies!) I rented a friend's renovated colonial house in Centro near Paseo Montejo for nine months to evaluate living in Merida. At the end it was a tough decision to make between deciding to stay in Mexico or return to Thailand. Inertia won out, and I moved back to Thailand, where all my stuff was.
However, I'm again re-evaluating things and will be returning to The White City in less than a week for a brief visit to refresh my memories and re-consider relocating again. I've been decluttering my life of physical things which would make a move much easier now.
Except for that nine-month period, I've lived in Thailand since 2001, starting in Bangkok and then moving down to Jomtien (Pattaya) with a few years in Hua Hin. Thailand has suited me well, but so did Merida.
Life in Thailand vs Mexico -- Merida in particular -- is overall pretty comparable. I really liked living in Centro in Merida. Even without a car. Bus service is easy to master, and now there's even Uber. Cost of living and health care are pretty much on a par. The MXN currency exchange rates can be worrying, but that's been the same with the THB, as well. Immigrations procedures are totally different, of course, but Mexico is not all that difficult to understand and adapt to.
For some individuals, though, like retired, single white males looking for abundant choice in young female (or male) accompaniment (the OP knows what I'm talking about), Mexico might not be their cup of tea. If you see a 70-year gringo man walking with a pert 20-year old Latina on his arm, it's his granddaughter, not his wife.
One big plus to Mexico is that you can actually own a house legally. Granted, in "restricted zones" (like Merida) you need to put the house in a trust. But, it's not like Thailand where you absolutely cannot legally own property other than a condo.
I felt really safe in Merida. Generally Americans think "Mexico" and they think "drugs, gangs, violence, murders," but so far, Merida has avoided most of that, being off the Narco Trail to the USA. I do wonder about the future of Merida if it continues to grow. As more and more folks from other parts of Mexico move and settle in, might they bring some of the criminal element from the rest of the country with them? <shrug>
Those are just some spontaneous thoughts I had when I read the OP. Not sure if he lives an urban Bangkok life or more rural upcountry. I'm a city boy at heart, and found Merida perfectly adequate.
Not sure if this is helpful, but here's a blog from my initial time in Merida: http://www.wpcoe.com/mxblog.htm