F16 and F18 fighter planes flew very close to the Cambodian border by mistake about 1pm on Thursday, air force chief-of-staff Air Chief Marshal Prachin Chantong said.
ACM Prachin said the fighters were seen flying only two or three kilometres from the Thai-Cambodian border in Si Sa Ket province.
This caused speculation they were testing the border at a time Thailand and Cambodia are engaged in a border conflict.
In fact, the jets were from the air forces of Thailand, the United States and Singapore taking part in the Cobra Gold 2011 exercise being held in the 2nd and 3rd Army Regions, he said.
ACM Prachin said aircraft taking part in the exercise should be flying at least 10km from the border, but a mistake caused the planes to approach to within two or three kilometres of the border.