Bangkok, Thailand — Thailand's biggest refugee camp has 10,000 more Kampucheans in it than anyone knew until a recent census. Most of them bought their way into the Khao I Dang camp, eight miles from the Kampuchean border, according to Western refugee officials who point out that new Kampuchean refugees officially have been stopped at the border for the past two years.
Despite these illicit entries, Thailand's overall refugee population decreased during 1982 from 193,000 to 169,000. New refugees numbered 11,261, more than half of them Vietnamese, compared with 43,000 in the previous year.
Six refugee camps were closed altogether and two others will do so at the end of this month. After that the population of 169,000 (84,000 Kampucheans, 76,000 Laotians and 9,000 Vietnamese) will be in six major camps.
Arrivals in 1982 declined by a welcome 74 percent; departures declined, too, although by a smaller amount. Just over 33,000 left Thailand for new homes in other countries.
Despite suggestions that the United States is operating a closed-door policy, more than half of the refugees (19,000) went to the US; 7,600 to France; 3,300 to Australia, and 2,000 to Canada.
The orderly departure program direct from Vietnam has expanded recently. More than 1,000 left Vietnam for the US in the past three months and departures are expected to be about 200 a week in months ahead.
A disturbing new factor adding to the refugee problem is the increasing birth rate among refugees. There were 8,239 births in 1982.
Family planning is not popular, especially with Kampucheans anxious to rebuild lost families. At one time there were attempts to force Kampuchean women to have injections of contraceptives. Thai officials at one camp refused permission for them to marry unless they had the injections, but those attempts have been abandoned, say international refugee agencies.
American refugee officials are now able to enter Thailand's most controversial camp to interview Vietnamese who are possibly eligible for resettlement in the US.
Thai authorities previously had denied resettlement opportunities to the 1, 800 inmates of ''NW 82,'' a key part of the harsh ''humane deterrent'' policy designed to deter refugees from entering Thailand.
Following unfavorable American press reports and statements by Congressmen about appalling conditions in the camp, the Thais relented and made the Vietnamese at ''NW 82'' eligible for resettlement.
Five Amerasians, wartime children of American fathers and Vietnamese mothers, are in the camp which is located in a border area exposed to recent military action.
Recent charges of refugees being forcibly repatriated have not been sustained , although voluntary repatriation is regarded by almost everyone as the ideal solution. Fewer and fewer of the refugees themelves, however, see it as a possibility as they are fearful of what awaits them in their homelands.
In 1982, 1,069 Laotians voluntarily returned to Laos. Many more Kampucheans chose repatriation although for them it was no more than exchanging a refugee camp in Thailand for one on the border.
Almost 9,000 of them made the change in 1982 with the bulk of them going to an area under the control of Prince Norodom Sihanouk, who heads the anti-Vietnamese resistance government.
Despite their misgivings many of the Kampucheans decided to go back to their own territory on the border after an emotional appeal for their support by the prince.
That repatriation has now declined to a trickle with not many more than 100 going in the past 21/2 months.
Those who did go earlier now form part of the border population of 300,000 Kampucheans who have no status as refugees.
They are living in great danger because war between the Vietnamese and their own guerrillas is going on around them.
More than 70 have been killed during the past six weeks and more than 200 severely wounded.
Relief workers and their own leaders fear for their safety as intense fighting goes on close to the shacks in which they live.
As nonrefugees they are not eligible for resettlement in other countries and are not even considered for it.
If the fighting gets worse they will inevitably flee into Thailand.