Thousands of highly paid government executives, and members of Congress, will be able to invest up to $12,712.50 this year in their tax-deferred thrift savings plan accounts.

Thanks to this month's raise, and a new higher contribution limit from the Internal Revenue Service, most workers will be able to invest more this year in stock, bond or treasury options of the savings plan. Rank and file workers got a 4.1 percent raise. Executive salaries went up from 18 percent to 25 percent.

The maximum individual contribution to a savings plan this year is $8,475. In 1990 the maximum contribution allowed by the IRS was $7,979. That limit doesn't include matching government contributions, which also are tax-deferred.

The nearly 1 million people under the new Federal Employees Retirement System can put up to 10 percent of base pay, up to the new $8,475 limit, in the savings plan. Those investing 5 percent get a matching contribution from their agency. For top-paid FERS employees, that match will be $4,237.50.

Workers who stayed in the old Civil Service Retirement System (mostly pre-1984 hires) can invest 5 percent in the savings plan, but without any government match. All investments and earnings are tax-deferred.

The higher investment limit most benefits FERS workers who are paid $84,750 or more a year. This month's big raises for nearly 8,000 executives pushed the Senior Executive Service pay range to a minimum of $87,000 and a maximum of $108,300. Most executives in the new pension plan will be able to contribute the maximum allowable and get the maximum match.

Even those under the CSRS system will be able to invest more this year because of the January raise.

FERS employees with a base salary of $84,750 or more should keep the contribution limit in mind when setting their payroll deduction contributions to the savings plan. They could lose some of their agency matching contribution if they reach the annual maximum too quickly. That is because they receive the matching contributions only on the first 5 percent of base pay contributed each pay period. Those who hit the annual limit before the end of the year will have their contributions, plus the agency match, stopped.

Employees have until Jan. 31 to decide how much they will contribute each pay period, and which options to invest in. Social Security Benefits

Social Security will have a free benefits fair Jan. 30 at the Silver Spring Armory. The 10 a.m. to 3 p.m. session is open to all. It will cover Social Security benefits and estimates, Medicare, Medicaid, aging and new laws, and pending proposals that would affect benefits. There will be a special booth for Spanish-speakers. For details, call Joe Hickman at 301-427-2650, Lorna Walters at 703-274-0262 or Chris Williams at 202-653-7093. Arabic Broadcasters

Voice of America is looking for Arabic-language broadcasters for its beefed-up Middle East broadcast services. Call Virginia R. Garner at 202-619-3117.