Reungchai Prayoonvech, deputy director of the Department of National Parks, Wildlife and Plant Conservation was nominated by the department's permanent secretary to succeed Khun Damrong, who had retired.
But yesterday, PM Yingluck nominated academic Dr Kaseman Jinnawasa, 52, for the position, and Cabinet quickly endorsed her man.
Thai media said that Khun Reungchai would have been likely to follow the aggressive lead shown by Khun Damrong but the position likely to be taken by Dr Kaseman could be more concilliatory.
Khun Damrong has set the Phuket property industry on edge with a campaign in the few months before his retirement to expose the wholesale theft of huge tracts of Phuket's Sirinath National Park.
There is no suggestion that the well-known resort and residential villa brand managements now operating around the park's borders knew about the suspected swindles, which are alleged to have taken place over several decades as doctored title deeds changed hands as many as 10 times.
The department is investigating each title case by case and it's likely there will be different outcomes for each of the investigations.
Years of inaction by the authorities and continuous malfeasance by corrupt officials have led to Phuket being at the frontline of efforts to save Thailand's national parks from further encroachment and, if practical, restore stolen parkland.
Dr Kaseman, regarded as an academic, takes over with the investigations of 14 properties bordering the Phuket park well under way and probes on 366 more suspect land titles due to begin today.
The department officers involved were meeting in Bangkok, before visiting Phuket.
In an editorial the Thairath newspaper applauded the stance taken by Khun Damrung in protecting Thailand's natural assets and questioned whether the Prime Minister's appointee would pursue the same aims.
Dr Kaseman, who obtained his PhD at the University of Notre Dame in the US, was once deputy director of the department, Thai Rath said.
However, he was seen as being inclined to take a moderate and conciliatory stance, the newspaper added.
One of the land titles being questioned by the department's investigating teams - all recruited from outside Phuket to avoid undue local influence - was yesterday found to be genuine.
With a second title still being reviewed by the Forest Department, management at the Imperial Adamas Beach Resort Phuket declined to comment.