Myanmar soldiers raided a settlement of temporary huts to detain the villagers, who had entered from the southern Thai province of Ranong to work on plantations illegally established in forests across the porous border.
The Thai military said they had begun talks with their Myanmar counterparts to secure the release of women and children and gain medical access to the villagers.
"We had talks last night and all of them are safe," Colonel Pornsak Poolsawad, of the Thai-Myanmar Border Committee said, adding the villagers had ignored warnings from Myanmar's authorities to leave the area.
Confirming the detentions, one of Thailand's deputy prime ministers, Yutthasak Sasiprapa, said he was confident that "all will be freed" and the problem "will be settled today".
Local media estimates said up to 500 villagers had been detained.
Thailand shares a 2,400 kilometre (1,500 mile) border with Myanmar and Ranong is a key crossing point used by workers from both sides.