The PM's deputy secretary on Tuesday explained why Prime Minister Srettha Thavisin's flight to New York to attend the 78th United Nations General Assembly from Sept 18-24 cost 30 million baht.

The prime minister flew to the US on a Thai Airways International (THAI) charter flight.

Natreeya Thaweewong, the PM's deputy secretary, was responding to recent calls by a political activist to look into why the flight cost so much.

The service offered an all-round-trip from Suvarnabhumi Airport to New York with a stopover in Tokyo.

Ms Natreeya, who handled the travel arrangements, said e-bidding was held to seek a reasonable price, adding the Royal Thai Air Force (RTAF) wanted 32 million baht to put on a charter flight service, while Thai Airways asked for 25 million.

But the amount Thai Airways wanted rose to 30 million baht due to fuel prices, so the price the RTAF set might have risen to 40 million baht, Ms Natreeya said.

Of the cost, 4.84 million baht was paid for aircraft-related expenses, 16.8 million baht was fuel costs, 1.47 million baht was for food and drink, 3.06 million baht was for ground services and 3.8 million baht was operation costs.

Ms Natreeya said around 50 other passengers who accompanied the premier on the aircraft, such as his daughter, paid for their own tickets and accommodation.

She said the government opted for a charter flight to avoid disturbing other passengers on a commercial flight.

A source also said the THAI flight only offered business-class seats for Mr Srettha and his entourage.