most everything you mention it true. The current repercussions from local government corruption is the reclaiming of developments illegally built on national forest lands, that illegal title deeds were issued for. The crackdown on these started with the last government, with data imagery made available by NASA of the USA, and their decades of satellite imagery, showing all lands, including national forest land before it was built on, and after images of it built on, with all these images in the public domain now, if you know where to look. Thailand is using these to reclaim illegally built on national forest lands.
there is no property tax on the property you personally live in, but there is commercial property taxes, and property taxes on properties you don't live in. Most condo developments also have yearly home owner fees.
I might add that any permanent fixtures you add to the land, like a house, or pool, etc. Become part of the property, owned by the land owner, meaning you can't destroy them, or take them with you when the lease ends.
you can not sell the lease at all. You are cancelled, and the new leasee must negotiate a completely new lease with the owner. That is why it is not an asset.
the lease has to be registered at the land office. After that the government has nothing to do with it. You are not added to any title, or deed. You also, as it stands now, can not sell the lease to anyone, whether they are Thai, or a foreigner. This detail is what is attempting to be changed in parliament, that would make the lease a tangible asset.
the "upon agreement, and with consideration" is the catch, and what makes it worthless as an asset. And, it's not about selling the land. It's about the inability to sell the lease on the land.
What you are doing, and have been doing visa wise works, and will continue to work given your situation. There is no reason to change. I know people that have been doing the same thing you are doing for over ten years with no problems. Don't overthink things just because of the building of a house with your wife. If you are that concerned though, and have the money, you could also consider an actual investment visa through the BOI. It fits your living here schedule.
because as the laws stand now it can not be considered an asset. Leases now are not transferable under the same lease agreements. This is in the process of being changed, making leases sellable under the same conditions, but hasn't been approved yet. Currently a completely new lease, and conditions is required, if the new lease is even approved by the actual owner of the land.