State media says clashes at Ayeyarwady region village left three dead, while local media say up to 20 civilians killed.
Thailand has expressed concern about the violence in many parts of Myanmar and called on its neighbour to take action and end the turmoil roiling the country since a February 1 coup.
Myanmar’s military has shown little sign of heeding the “Five-Point Consensus” agreed among the Association of Southeast Asian Nations (ASEAN) in April, which calls for an end to violence, political talks and the naming of a regional special envoy.
“We have been following developments in Myanmar closely with much concern, especially incidents of violence in many parts of the country,” Tanee Sangrat, spokesman for the Thai foreign ministry, said in a statement on Sunday.
He reiterated a call for an end to the violence, the release of all detainees and the “concrete implementation of the Five-Point Consensus” as soon as possible.
The military has failed to impose control since seizing power from elected leader Aug San Suu Kyi, who is among more than 4,500 people detained since the coup. A rights group says at least 847 people have been killed, but the military disputes that figure.
Meanwhile, daily protests against the military have evolved in parts of Myanmar into armed uprisings while decade-old ethnic conflicts have flared anew.
Opponents of the military have voiced frustration at the lack of tough action by ASEAN and say the meeting of two representatives of the group with coup leader Min Aung Hlaing on Friday gave him greater legitimacy but brought no benefit.
Thailand has a longer border with Myanmar than any other country and fears the conflict could bring a flood of refugees. Its government is itself led by a former army chief who seized power in a coup before holding elections.
“Much of what Thailand has done may not have been made public, as we believe that quiet and discreet diplomacy between neighbours would be more effective and in line with traditional Thai diplomacy,” Tanee said.