Five people were wounded in the explosion believed caused by a bomb at a guest house in the Myanmar border town of Myawaddy.
Col. Photsawat Tangchui, a police chief in Thailand's border district of Mae Sot - across the Moei River from Myawaddy - said that a bomb exploded in a room at the Shwebyisaya Guest House, located near the Thai-Myanmar Friendship Bridge linking the two countries.
He said two hotel staff were hurt.
Maj. Gen. Surachet Chaiwong, the Thai army commander for Mae Sot, said a Myanmar counterpart told him that a cooking gas tank at a small hotel had exploded, injuring one person.
There was no immediate evidence linking the incident to the pro-democracy protests in other parts of Myanmar that have been suppressed by the ruling military.