Sure they can, but most probably they have not a well developed software that automatically shows them a red flag and when you have a line with 10 people waiting it's normal to go in the easy way and just stamp the new pass. I did enter after Ed visas with old and with a new pass and always had questions with the old one and a very fast processing with the new one... Sure somewhen in the future they will update their software and this approach will become useless... So better try to get a long term solution.
And this is why you didn't face a problem, cause you didn't use the entire length of your visas/extensions, so obv when smo enter and stay 1 month and go out is not about working here. Problems occur when you leave after full stay+extension and visa run for 1-2 days... Additionally you re most probably over 50 and qualify for a retirement visa, so it's less likely to work illegally...
For sure it's getting harder and harder to stay long term on Ed or TV or similar. If you have a long relationship just marry if not just search for a second country nearby and split it
*****
. And change your passport every year, I never had any problem with a fresh new passport and was asked a ton of questions while LEAVING Thailand after the COVID with a passport full of COVID extensions + Ed visa... New passport did work well at least 1 year ago...
I did this visa 1 month ago switching from tourist to non o in Phuket. They required bank account, but i was told that the requirement for 400k 2months+ is for the extension, as my 400k were transferred 40 days before the application. Additionally, there is not requirement for this money to come from abroad, in my case i just did transfer them from my wife's account. Visa application was approved. The best is just to call them.
The e visa now is just emailed peace of paper, so you can count the extra days in the sea as well. I did need about 3 weeks to get it. But there are many docs required.
It's not very possible to get problems with just 1 ed visa, if you go for it just make sure that 1) you will not leave the country 1 year and 2) after the visa expires you will leave the country for at least 2-3 months. However, it's always possible to face some problem with Ed visa, rules are stricter lately, and it's not for free as well, it will cost you probably around 50k thb total for 1 year. Multy entry tourist visa is the best if you can get it.
I really doubt you will be able to get the house as it was presented to you while buying. If I were you, I would just try to make him transfer whatever is built and finish by myself...