Construction magnate Premchai Karnasuta was arrested along with three others on Sunday night by rangers who stumbled upon their camp in a wildlife sanctuary in western Thailand.
They seized guns, ammunition and animal carcasses including a rare black leopard, leading to police charges for hunting in the national reserve and poaching a protected species.
Premchai is the president of the publicly traded Italian- Thai Development, a Bangkok-based company that helped build Thailand's Suvarnabhumi airport and the city's skytrain public transit system known as the BTS.
Amid mounting outcry junta leader Prayut Chan-O-Cha said whoever tries to interfere in the case "risks being punished".
Also Read
If he is found guilty "it's not possible to help (Premchai), guilty is guilty no matter how big he is," he said.
Prayut's comments followed the leaking of an unverified audio clip purporting to be from the night of Premchai's arrest in which an unidentified voice discusses the influence of "senior people" in the context of a "loophole in the law".
"I can assure you that no-one can lobby to clear this case," Police General Srivara Rangsibhramanakul told reporters today.
The tycoon's case comes as a separate scandal swirls over the junta's number two, Defence Minister Prawit Wongsuwan, who is being investigated over a collection of undeclared luxury watches.
The Thai junta seized power in 2014 vowing to expunge graft from politics and society.
But critics say it has failed and is clinging onto power too long.
Premchai's predicament has deepened over the week. A police raid on Wednesday on one of his Bangkok properties found weapons and ivory tusks.
A petition on Change.org supporting a thorough investigation garnered more than 83,000 signatures by Thursday afternoon while the national police chief reassured the public that Premchai's status as a "high-profile businessman" will not impact the police.
The Thungyai Naresuan national park where Premchai was arrested is in tourist-friendly Kanchanaburi province and hosts wild elephants and tigers among its endangered species.
The slain animals at the campsite were a black leopard, a Kalij pheasant and a red muntjac or barking deer -- protected species under Thai conservation law.
General Surasak Karnjanarat, Minister of Natural Resources and Environment, on Thursday added his weight to the investigation saying "it is quite clear that they did something illegal".
Disclaimer: No Business Standard Journalist was involved in creation of this content