The Supreme Court ruled yesterday that some workers injured in the Virginia and Maryland suburbs may first collect workmen's compensation benefits from those states and later get money from the District's more generous compensation plan.

The court's 7-to-2 decision reverses a lower court ruling and offers the prospect of additional financial awards to thousands of area workers employed by firms that operate in both Washington and its suburbs.

The ruling came in the case of Halley I. Thomas, a Washington Gas Light Co. construction worker, who lived in the District, but was injured on the job in Arlington.

Lawyers for the utility had successfully blocked Thomas from securing additional benefits from the District after he had exhausted his $62-a-week benefits from Virginia. They had argued that under Virginia law injured workers could collect benefits from only one jurisdiction.

But the court, in overturning a 1940 decision, rejected that view yesterday.

The majority opinion, written by Justice John Paul Stevens, held that "a state has no legitimate interest . . . in preventing another state from granting a supplemental award" to an injured worker.

The exact implications of the ruling were unclear yesterday, but one government official said it could lead to chaos in pricing the insurance that employers carry to cover work-related injuries."This makes it very difficult for employers and insurance carriers to find out the extent of their liabilities," said James DeMarce, a Labor Department official.

Washington Gas spokesman Paul Young, said his firm was "disappointed" in the ruling.

Attorneys for Thomas hailed the decision as a victory for workers across the country who may be ignorant of their right to shop around and collect the highest benefits for which they are eligible. Current maximum benefits paid by the District are about twice as high as those paid under Virginia and Maryland law.

"I don't think anyone has a headcount of the number of people who are potentially affected by this decision," said DeMarce, executive assistant to the director of workers' compensation programs.

As part of the 22-page opinion granting the right of workers to collect compensation benefits from more than one jurisdiction, the Supreme Court ordered a lower court to consider what Thomas may collect in benefits.

Between 1971 when he was injured and 1974, Thomas received the maximum $24,800 in benefits then allowed under Virginia law. When those benefits expired, Thomas, who was then adjudged permanently and totally disabled, applied to the District for additional compensation.

Washington Gas, through a series of administrative and court challenges, fought the action, although a Department of Labor administrative judge held that Thomas was eligible to receive the added payments from the District.

Although the court's ruling allows Thomas to receive further benefits, there is a restriction on the award from the District. The $24,800 Thomas has received from Virginia will be subtracted from any award he is granted under the District plan, his lawyer said.

Workmen's compensation benefits have been a highly controversial issue in the District, where the City Council recently voted to cut the payments schedule under intense pressure from business interests. The businessmen said their insurance payments are second only to those of Alaskan businesses. For example the maximum payment an injured worker can receive under the District plan is $426 a week, compared to $241 in Maryland and $199 in Virginia.

Last month, after an intense lobbying campaign by the Greater Washington Board of Trade, the D.C. City Council passed a bill that rolls back and freezes for five years the maximum payment to $396 a week. That bill, signed by Mayor Marion Barry, is awaiting final congressional action.