Thailand is moving to force the sale of land worth about 14 billion baht ($417 million) as it cracks down on foreigners who evade an ownership ban by holding property via local proxies.

Prime Minister Anutin Charnvirakul said Monday that his government is stepping up investigations into such arrangements and tightening scrutiny of new purchases.

Foreigners are prohibited from owning land in Thailand, but some use Thai nominees to circumvent the restrictions, a practice under growing scrutiny after a series of cases in major tourist and business centers.

Authorities are targeting about 5,467 rai (2,161 acres) of land linked to suspected nominee arrangements, according to Somchai Leelanoy, director-general of the Department of Lands. That is an area roughly equivalent to 1,225 standard soccer fields.

Anutin ordered officials to accelerate investigations of high-risk cases by December and enforce laws requiring illegally held land to be sold. Authorities will also seek to prevent new nominee arrangements from entering the property system, he said at a briefing Monday.

The government is tightening checks on buyers as part of the effort. Individuals purchasing land for more than 2 million baht, or property with an assessed value exceeding 5 million baht, will face background checks, Somchai said.

Thai nationals married to foreigners will have to show that money used to purchase land belongs to the Thai spouse. Companies buying property will face scrutiny of their shareholders and sources of funds and be required to provide supporting documents under Thailand’s land laws.