Of the 53 people held, 37 are believed to be from the Rohingya minority, with the remainder from Bangladesh — a source of increasing numbers of migrants arriving on Thai shores.
Twenty-one of the group are aged under 18 and some are as young as five, according to the chief of Takua Pa district in Phang Nga province, Thailand.
"The group were from Myanmar and Bangladesh," said Mr Manit Pianthong. "They arrived on boats and were taken in three trucks into Takua Pa before dawn on Monday" for transit through to Malaysia.
"We had already set up checkpoints as we had information they would come," he added, explaining the trucks were forced onto a side road where the drivers fled, leaving the migrants behind.
The migrants have been taken to be interviewed by social workers to determine if they are victims of trafficking.
"If they are found to be victims, they will be witnesses in a human trafficking case and will be put in shelters ... but if not, they will be charged with illegal entry," Mr Manit said.
Thousands of Rohingya, a Muslim minority group not recognized as citizens in Myanmar, have fled deadly communal unrest in Myanmar's Rakhine State since 2012. Most have headed for majority-Muslim Malaysia.
Myanmar views its population of roughly 800,000 Rohingya — described by the United Nations as one of the world's most persecuted minorities — as illegal Bangladeshi immigrants and denies them citizenship.
Rights groups say the stateless migrants often fall into the hands of traffickers.
They have also criticized Thailand in the past for pushing boatloads of Rohingya entering Thai waters back out to sea and for holding migrants in overcrowded facilities.
Thailand said last year it was investigating allegations that some military officials in the country were involved in the trafficking of Rohingya.