Virginia Del. Robert L. Thoburn (R-Fairfax) sat in a hotel bar the other night, sipping a Coke and eating chocolate ice cream -- hardly the image of a state legislator out on the town at day's end.

But Thoburn, a 49-year-old fundamentalist minister and business man, has proved for two years in a row that he is not one to follow the pack -- on the General Assembly floor or off.

Being different has become his style. "I take positions that are considered suicidal," he boasted the other day.

Indeed, during this session, scheduled to end today, Thoburn voted against several key measures that had near unanimous support in the Northern Virginia delegation. He alone opposed a bill giving $50 million state funds to localities without raising taxes. He also opposed a new law school for George Mason University and a one-cent sales tax for Metro transit operations, causes dear to many in the Washington suburbs.

Thoburn says he took all those stands because as a conservative he is convinced that the bills will merely increase the amount of governmental regulation. That's a concern often voiced by many members of the assembly from other regions, not often by Northern Virginians.

Long before he arrived in Richmond, Thoburn's reputation as a conservative was well known. Virginia populist Henry E. Howell called him "the Siamese twin of a caveman" the day he was elected, saying his conservatism would be an embarrassment.

True to the polite tradition of Virginia politics, Thoburn's colleagues here are more circumspect in discussing Thoburn's role in the 140-member assembly. "Thoburn is unquestionably the most ultra-conservative person to serve in the General Assembly this decade," says Del. Richard L. Saslaw (D-Fairfax).

Del. Gary R. Myers (R-Alexandria) says that Thoburn is not the "rightwing crazy kook" that many lawmakers once believed him to be but Myers agrees that many of Thoburn's statement's have given him a unique reputation among the members of the General Assembly.

Thoburn yesterday reaffirmed statements that brought a flurry of publicity when he ran for the House of Delegates in 1977, saying that he still believes rapists should be executed, that men who seduce young women should be forced to marry the woman (if her father agrees), that public schools in Virginia are a bad idea and that the government should not help poor people.

Thoburn, who has eight children and runs the back-to-basics Fairfax Christian School, says his philosophy remains the same as it was when he was elected in 1977: to get rid of as much government as possible and allow the family to take over direction of American life.

Despite his views, which raised many eyebrows in a legislative body considered to be one of the most conservative in the country, Thoburn is well-liked by his colleagues. "He's a pleasant kind of guy," says Saslaw. "He seems to have mellowed," says Myers.

Thoburn said today he finds himself voting less often against the other 99 members of the House than he used to.

"I used to worry about every single bill. But I've found that 98 percent of the stuff that goes through the door down here doesn't make any difference. But I still vote no on all the important things," Thoburn said.

Thoburn, a staunch foe of abortion and the proposed Equal Rights Amendment, said his greatest legislative accomplishments have been to support a bill that stops the state from regulating church-run child day care centers and to help kill General Assembly approval of ERA.

Thoburn managed to pry his first bill out of a committee this year, a measure that would have called for an advisory referendum on whether the legislature should pass the ERA. That success proved to be shortlived as the full House quickly voted to return the bill to committee.

Such views, Thoburn agrees, make him a controversial figure, but not an unpopular one. "My election proves anybody can get elected," he said with a smile, draining his Coke.