My wife got a letter from the tax office to pay a visit to morrow. The can not see that she has pay the tax on the lease amount. On the contract I pay the lease (rent) for 30 years all at once. She thinks the tax is 5%. We pay some tax at the land office when purchase the land, but that is presumable an other tax.

Has anyone else been demand to pay this? It is 4 years since we put up the lease.

How about this:

Land and House tax Act B.E. 2475:

For individual property owners; if they lease out their property Building and Land Tax shall be collected at the rate of 12.5% of the yearly rental according to the lease agreement or the annual value assessed by the Land Department, whichever is higher. The annual assessed value means the amount of money which the property may reasonably be gained from the lease out of a property for each year if the property is offered for lease.