PTT's ranking in 2014 Fortune 500 dropped from the 81st in the previous year to the 84th, though it remained the only Thai company on the list of top 500 global companies.
The national oil and gas company was first enlisted in 2011, being the 128th among the top companies then. In 2012, the ranking advanced to the 95th.
The ranking is determined largely by revenue in the past year, denominated in US dollar. PTT last year experienced a fall in revenue last year while the Thai baht also weakened against US dollar.
In 2014, it ended up at the 84th with the revenue of US$92.56 billion.
Pailin Chuchottaworn, the company’s president and CEO, thanked all executives and employees for their hard work in sailing the company through hardships.
"The inclusion of a Thai company reflects the country's ability in securing confidence from local and foreign investors," he said.