What is the best long-term visa option for a 38-year-old expat planning to holiday in Thailand?

As people correctly pointed out another option would be the 6 month METV <-Multi-Entry Tourist Visa.

That visa is valid for 6 months from the date it's issued, it's good for unlimited entries during the validity, each entry gets you stamped in for 60 days and can be extended once for 30 more days at the immigration office for 1900baht.

The down side of this visa (at least now with the covid shit show still ongoing) is the difficulty in bouncing out and back to activate another entry on the visa. The rule is you have to stamp in and out of another country to stamp back into thailand and with all the land borders closed you have to do that by air, meeting the entry requirements of the country you fly to and then meeting the entry requirements of thailand to get back in again too.

It is possible to stay almost 9 full months on a 6 month METV though if you plan the dates you bounce correctly and if you exit/re-enter one final time just before the visa sticker itself expires to get the last 60 day entry stamp and then extend that by 30 more days.

Good luck with it I think you have your options outlined in the post (y)

Tourist 60 days plus 30 day extension

If you really want to stay here long term then you should look into the Elite Visa.

I have a 60 day multiple entry, validity 6 month

Get married 😋

IF you have no intention of staying here past your holiday time you could get a Special Tourist Visa which is good for a stay of 9 months (in 3 month increments) you arrive and get 90 days, then you apply for a 90 day extension and then you can apply for one final extension of 90 days after that

BUT

Then you go back to where ever it is you come from or at least leave the country AND the STV cannot be switched to another visa type inside the country

It's strictly a come, be a tourist for 9 months and leave sort of visa option.