Well, this is the normal BS to be expected here! Originally, 10 years ago, I had a lease drawn up with my Thai "daughter" as the owner. First I got wacked up for around 35,000 Baht to register the lease. I paid up and shut up. 4 years later my daughter received a demand letter for back payment of the outstanding tax due to the Tessaban. 15,000 Baht owing for 4 years = 60,000 Baht! No getting around it, no negotiation, just pay up or else we will take you to court!
I should point out here that ALL of this was originally drawn up by a well known Thai legal company in Bangkok, whom neglected to inform me of ANY of this.
I also had a contract drawn up originally with my daughter to the effect that she borrowed the capital from me to buy the house. This also incurred some tax somewhere along the way to register it I believe. The contract was never part of the process with Land Department, and they never queried her about where the money came from.
Following the payment of the outstanding tax I found out that the reason was because the lease is regarded as a commercial business, plus my daughter should also have been paying tax on the lease money, regardless of whether or not I paid her.
We tore up the lease and my daughter went and had my name removed from the Chanote, for I think it was 80 Baht. She then went to the Tessaban where she paid 2 years rate of 9 Baht, plus 1 Baht "fine" for each year outstanding, total 20 Baht!
Since then I have gone every year and paid 9 Baht, as I did just yesterday
And these people want to have a submarine to play with!