US Charge d'Affaires Michael Heath rejected as untrue a string of rumours ranging from the United States building a secret missile base at a new compound in Chiang Mai to pressuring the Thai air force to buy stealth fighter jets from the country.
The US envoy, who currently serves as the US diplomatic mission leader, responded to the rumours while meeting with reporters at the US ambassador's residence in Bangkok.
He said the new consulate general being built in the northern province of Chiang Mai has a price tag of US$280 million (9.3 billion baht) due to high-security requirements and the use of green technology.
US embassies or consulates are designed to be highly secure and able to protect against explosions, he said. The new campus is not designed or built to house any "secret or missile base", he insisted.
According to Mr Heath, the Chiang Mai Consulate General is looking after about 17,000 American nationals living in the northern region.
He also denied a rumour that David Eubank, founder of Free Burma Rangers, was sent by US authorities to provide weapons training to Karen villagers against Myanmar forces.
Mr Eubank, a former US Special Forces officer, became a missionary after retirement and the Free Burma Rangers is a relief organisation that provides humanitarian aid, not weapons, he said.
Mr Heath dismissed as false, reports circulating on social media that Gen Mark A Milley, chairman of the Joint Chiefs of Staff, made a secret visit to the kingdom and met Gen Chalermpol Srisawat, chief of Thailand's defence forces.
In truth, Gen Chalermpol and his delegation, invited by the Pentagon, made an official visit to the United States last December to discuss cooperation in education and training among issues, he said.