The United States' request to increase military activities at the naval airport in Rayong province proves it wants to be more active in the region, military authorities say.
The US wants to use U-tapao military airport for its Humanitarian Assistance and Disaster Relief operations and for climate studies by Nasa.
The US will increase its activities at U-tapao so that it may use Thailand as a base in response to the growing Chinese military presence in the Asia-Pacific region, the authorities said.
US activities have been carried out at U-tapao airport for some time, with some of them unreported.
"The US built U-tapao airport and has been using it under a memorandum of understanding," a Thai military source said. American soldiers and airplanes visit U-tapao airport all year long.
"There are large and small-scale Thai-US military exercises that involve all armed forces, as well as classified drills."
The source was referring to the 1983 MoU signed by the Royal Thai Navy and the Joint United States Military Assistance Group.
The source said several factors have prompted the US to revive its Asia-Pacific presence after focusing on the Middle East for the past decade. The factors include China's military expansion in Asia, the South China Sea maritime territory dispute and nuclear cooperation in recent years between Myanmar and North Korea.
Ties with Thailand appear to be growing closer.
US Secretary of Defence Leon Panetta sought bilateral talks with Defence Minister Sukumpol Suwanatat during the Shangri-La Dialogue in Singapore on June 1-3.
The meeting was followed by a visit by Gen Martin Dempsey, chairman of the US's Joint Chiefs of Staff, as the guest of Supreme Commander Thanasak Patimaprakorn on June 4-5. Also, the US Navy invited navy chief Surasak Rounroengrom to visit America last March.
It was the first visit by a Thai navy chief to the US in 19 years.
The US discussed its planned activities at U-tapao in all the meetings with the military authorities.
"This shows the US is returning to the region in response to the increasing power of China and to develop ties with Asean before it leans on China," the source said.
Gen Dempsey denied the US had any hidden agenda.
Gen Nipat Thonglek, director of the Office of Policy and Planning under the Defence Ministry, said the US allowed Thailand to control its activities at U-tapao airport and Nasa would open its work there to scientists and students.
However, he said world powers were rebalancing their influences in the region and the Thai military always weighed its strategies with consideration to its relations with both the US and China.
"As we are a small country, this is all we can do.
"We are only a pawn of the world powers in their counter-balances," Gen Nipat said.
The opposition Democrat Party yesterday repeated its call for the government not to let the US increase its activities at U-tapao airport.
Democrat deputy spokeswoman Mallika Boonmeetrakul said approving the US's request for increased activities at U-tapao airport without seeking parliamentary backing would violate the constitution.
She added that some Democrat members wondered if the government would seek a US visa for self-exiled former prime minister Thaksin Shinawatra in exchange for allowing the US to use U-tapao airport.