Just don't visit the same countries all the time and get repeated SETVs from the same place. She may have a problem doing it for 2 years as that is probably 6 or 7 in 2 years, depending how long her holidays outside are. Just see how it goes. METVs would make a lot more sense for that length of time.
LOL Yes we are on the same page here. I wrote it wrong (corrected). No funds for a single entry. Only place that used to do multi entry for a Thai child with proof of the 400k was Penang. Not sure if that loop is closed already or not. I would get a single entry and then extend for a year with proof of funds for the child. Too easy as he is already the legal father.
Why do you need to get a year outside? Just get a 90 day and then extend it for a year when you get back to Thailand. Put 400k in the bank. You are already legitimized (which is the hard part). Then get a single or multi re - entry permit, if you want to come and go. Will be 5700 per year. 1900 + 3800. I realize you don't wan't to show proof of funds. But it is only 400k and you don't have to use it.
Legally it is the responsibility of the Landlord to register his Tennants within 24 hours of their arrival. But if the Tennant is the one applying for an extension then you could always go in person to lodge the TM30 and pay the 1600 fine and arrange to get it back from the Landlord later. (or not get it back if he didn't know of the requirement and you didn't tell him when you arrived).