Thai Foreign Ministry spokesman Tanee Sangrat said the warning shots on Thursday were used to signal boats for inspection due to the lack of official coordination method on the section of the Salween River where Thailand and Myanmar shared a border.
"Its a misunderstanding, the Thai border patrol police hired a villagers' boat to carry things and they were not wearing their uniforms," Tanee said.
"The Myanmar checkpoint saw the boat pass by without being inspected so they fired shots into the air to signal inspection and now both sides have spoken and come to an understanding with each other," he said.
Thursday's shooting took place near the Thai village of Tha Ta Fung in Mae Hong Son province, near where thousands of ethnic Karen from Myanmar fled military air strikes last month.
Thailand prevented most from entering its territory and tens of thousands are sheltering in the jungle on the Myanmar side. Humanitarian groups say Myanmar forces have also opened fire on boats carrying aid to the displaced in recent weeks.
A spokesman for Myanmar’s junta, which seized power nearly three months ago, did not answer phone calls seeking comment on the incident.
The Thai Ministry of Defence said all agencies under the ministry and the armed forces had been instructed to "be ready to handle problems and the impact from the violent situation and fighting in border areas."
The two security sources said no one was injured in the shooting at the boat, which had hoisted the Thai flag.
"The Myanmar military unit was concerned about boats sending supplies to their opponents on the other side so they signalled the boat for inspection," one of the sources told Reuters, adding that Myanmar officers had searched the vessel.
Jumi, 49, a restaurant owner in the area, said the shots were fired into the water beside the boat on the Salween river.
"People are very frightened by these shootings and they don’t want to take their boats out," she said.
The military has attempted to crush protests across Myanmar against its Feb. 1 coup, killing hundreds and fighting with ethnic groups along the border has also escalated.
Southeast Asian leaders, including Myanmar’s junta chief Min Aung Hlaing, are meeting in Indonesia on Saturday for talks on the crisis, which analysts fear could turn into an all-out civil war.
Some of Myanmar’s myriad ethnic armed groups, including the Karen National Union (KNU), which controls territory on the Thai border, have vowed to back the protesters and help overturn the coup.
Padoh Saw Taw Nee, the KNU's head of foreign affairs, said in a message the shooting showed Myanmar’s military was "very aggressive and arrogant".