via Bangkok Post, 06 Mar 2019: I think the editorial is overly critical of the Fine Arts Department in this case, and also is inaccurate in saying the site is under world heritage nomination as if the process is well underway. The site is definitely being considered for nomination by the government, but no submission to Unesco has been made.
The eager petroleum exploration company is Eco Orient Resources (Thailand) — a subsidiary of Hong Kong’s Eco Group. Eco Orient Resources applied for and received permits to search for petroleum in Si Thep district of Phetchabun in 2004. The firm now seeks to begin operations. An Environmental Impact Assessment (EIA) is due in April, and Eco Orient Resources is promising many measures that it says will mitigate noise and the ugliness of drilling rigs.
The site where this drilling is supposed to begin later this year is the northern part of the historical part. Khao Klang Nok is a colossal Buddhist monument. Archaeologists generally describe it as a temple, but by any standards it is huge. It dates from the Dvaravati period, or the 6th to the 11th century. The stupa of the temple is widely known and a destination for tourists, mostly Thais.