The department said there are title deeds for the land in Nakhon Ratchasima’s Pak Chong district which confirm Mr Tarit's legal ownership rights.
An anti-government group had claimed that Fiore Park Home Stay and its surrounding property, which belongs to Mr Tarit, encroached on a forest reserve.
People’s Democratic Reform Committee supporters in Nakhon Ratchasima on Thursday besieged the resort in tambon Nong Nam Daeng, accusing Mr Tarit of holding "unusual wealth" by owning the luxury resort.
They called on the Royal Forest Department to take action on the issue.
The department’s Forest Management Office Region 8 director, Somwang Ruengniwatsai, said his team had already completed an examination and field measurement of Mr Tarit's land and found the total land area is four rai, the same as that stipulated in the title deeds.
"The land survey and measurement have confirmed that there has been no forest encroachment by the resort as accused," he said.
"The resort has the title deeds, which were issued by the Land Department under the Interior Ministry, which means it does not encroach on the forest reserve zone."
He explained that the title deeds were issued since 1991 and Mr Tarit's wife, Wassamon Pengdith, purchased the land in 2012. There are seven structures built on the land.
However, Mr Somwang refused to comment on whether the title deeds were issued correctly, saying only that the process of issuing deeds falls under the authority of the Land Department, not his agency.
Mr Somwang added that other people holding state-guaranteed land ownership documents in the area indicates they were living there before it was declared a national park or reserved forest.
Mr Tarit’s land is located near Kho Sied-Ar, Pa Khao Nok Yoong and Pa Khao Ang-Hin national reserve forests, which were announced protected zones in 1964 and cover more than 100,000 rai.
Meanwhile, the Central Administrative Court on Thursday ruled in favour of the Department of National Parks, Wildlife and Plant Conservation in its move to demolish illegal resorts which encroached on Thap Lan National Park in Prachin Buri province.
The court said forest officials have the full authority to demolish the illegal resorts.
Owners of Pha Ngam resort in Na Di district filed a court complaint in 2011, demanding suspension of the demolition until an Appeal Court verdict is read.
The resort owner lodged the appeal after Kabin Buri Court ruled the resort encroached on the national park. The owner was seeking a suspension of demolition while the appeal was heard.
But the Central Administrative Court rejected the request, saying forest officials have full authority to carry out the demolition as there was irrefutable evidence that the resort was located inside the national park.
Thap Lan National Park chief Thewin Meesap said he would wait to see whether the owner lodges an appeal with the Supreme Administrative Court before taking action to continue work on the resort demolitions.