By Jonathan Head
BBC News, Bangkok
Thai authorities insist the Hmong in Thailand are economic migrants
Aid agencies in Thailand have expressed grave concern over the fate of around 1,000 ethnic Hmong refugees who have been deported back to Laos.
The refugees were returned across the border last weekend after taking part in a protest over their living conditions in Thailand.
The Thai authorities say that the refugees went back voluntarily.
However, human rights groups believe some, who face possible persecution in Laos, were forced to return.
Thailand's reputation for generous hospitality towards tourists does not extend to refugees.
Hundreds of thousands of people have come here over the years, fleeing war and poverty, from Cambodia in the 1970s and 80s, and more recently from Burma and Laos.
They are accepted - but confined to squalid camps.
UN agencies and journalists are usually denied access to them and at times the refugees are thrown back over the border.
In the 1970s, thousands of Cambodians are thought to have died after being forced back through minefields by Thai troops.
Now aid agencies fear for the safety of the ethnic Hmong refugees who were sent back at the weekend.
The authorities here insist they are just economic migrants who went back willingly but among them are remnants of the rebel army that fought communist forces with US-backing during the Vietnam War.
Some 8,000 Hmong have been living for years in a sealed-off camp in northern Thailand.
The UN's refugee agency has expressed concern that the deportation was carried out in secret.
Some families have reportedly been split up, and little is known about how the deportees are being treated in Laos, which has a record of harsh repression of any anti-government forces.