Reader question: Does Thai woman lose right to own land after marrying a foreigner?

I found that great link too. If I understand correctly, a Thai can also buy land during marriage with a foreigner, as long as she does so with money/resources that she already owned before the marriage was concluded. After all, those funds/resources have never become part of the matrimonial community of property, so that it is 'logical' that the land purchased with them does not fall into that community either.
Where Tino uses the word (ever), this could cause confusion again, since it evokes an association with 'a very long time ago' in me. You might as well, or better, read there: (now or ever).

Such a law has been in place for a while (less than 1-2 years?) but dual nationality has not been a problem for Thailand for many years. You may give up your nationality, but it is not an obligation. Strangely enough, there are still many old stories going around, even among Thai officials, and then you get ghost stories that a Thai should not have multiple nationality. Nonsense, for example there are plenty of famous Thais with multiple nationalities. From the Netherlands' perspective, multiple nationality is a problem with exceptions such as "married to BP of that nationality" and "disproportionate financial consequences if nationality were lost (related to inheritance law, among other things)".

And since a Thai, like other Thais, can simply buy land, a house, etc., there is no problem with purchasing land. As Tino indicates, they want a statement that the purchase was made with money from the Thai. I suspect purely to emphasize that someone without Thai nationality would not be able to claim (for example after the death of the owner).

Both topics (nationality and land ownership) have been discussed separately here and elsewhere, I couldn't suppress a small smile when I saw the question. I wonder if we will ever get rid of the Indian stories and “a cousin of an acquaintance of my Thai partner's girlfriend's neighbor says that”. 555

It does not state at all that she is not allowed to buy land if she is married to a foreigner. There must only be a statement from both partners that this purchase is made in the personal name of the wife and is not part of the common property. That's all.
Just like Tino wrote before. Same site by the way.

Sounds exactly what you're saying.
Here the form:
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https://www.samuiforsale.com/other-miscellaneous/land-purchase-letter-of-confirmation.html
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This joint statement goes on to say: 'In this case it is not the Land Department's policy to investigate the actual sources of funds.'
In other words: legally, what you have stated together applies, the actual situation is not important. It may sound a bit strange, but it is very common and it is called a 'legal fiction' where any evidence to the contrary is not honored. Just like the tax authorities who assume that you make a 4% return on your savings.