The case of arbitrarily building a house on agricultural land is an act of using land for the wrong purpose and will be subject to administrative sanctions.
Article 10 of Decree 123/2024/ND-CP stipulates the penalty for arbitrarily changing the purpose of using other agricultural land as follows:

Note: The act of converting agricultural land that is not rice-growing land or non-forestry land to non-agricultural land within the administrative boundaries of a ward or town shall be subject to a penalty of twice the corresponding penalty.
- Remedial measures:
+ Forced restoration of the original state of the land before the violation, except for the case specified in Clause 3, Article 139 of the Land Law.
+ Forced to return any illegal profits gained from committing the violation.