Hi,

I signed last year a leasing contract for my Thai gf for a land, now i want to build on it my house, do i need his authorization, does she has to sign some papers to get the building permit ? What i have to do exactly ? Thanks a lot for your help !

I really do not understand whether your GF or someone else is the land owner, "The Letter", but it doesn't matter since you asumably have signed a land agreement with the land owner with the intent to construct a house. In that case you already have the permition and not further approvals are not required from the land owner.

On the other hand, should the intent of the land lease had been for e.g. agricultural use then you will need an approval from the land owner.

As said, if the landowner has given you a long-term land lease that has been registered at the land office and recorded on the back of the title deed (Chanote) then all you need is a building permit in your name. If this is agricultural land you may not be able to get a building permit.

OP - unclear from your post who's the landowner and lessee and (depending on that) what / why you signed anything?

Anyhow, what does the lease say about building?

[most tessabaan will require a copy of the lease stating you are entitled to apply and have issued a buildingpermit in your name, in addition to a copy of land title with lease registered