Charles Johnson sank a fallaway 25-foot jump shot at the buzzer to give the Washington Bullets a 138-136 double overtime triumph over the San Diego Clippers tonight in a game that marked the return to NBA action of Phil Chenier after a 13-month layoff for a back injury.

The Bullets trailed by 20 points late in the third quarter but rallied behind 16 fourth-period points by Larry Wright and sent the game into overtime on Greg Ballard's two foul shots with 13 seconds to go.

Lloyd Free, who had 45 points for the game, forced a second extra period on a 20-footer with eight seconds to go in the first overtime.

In that second five-minute period, Elvin Hayes tied it at 136 with a free throw 28 seconds before the buzzer. Then, after Free missed a driving layup over the outstretched arm of Hayes, Johnson charged to the other end of the court.

He looked to the Bullet bench and was told to shoot by both Coach Dick Motta and assistant Bernie Bicker-staff. Johnson replied with a high arching shot that went through the net as the buzzer sounded. Johnson wound up on his back, sprawled out of bounds along the left sideline.

Washington came back in regulation behind a makeshift lineup that included Chenier, Dave Corzine, Wright, Ballard and Bob Dandridge. Chenier played 21 minutes, scoring six points and did a decent defensive job on Free. Washington was without injured Kevin Grevey and Mitch Kupchak.

Dandridge was ejected with his second technical foul in the first overtime and Hayes, who had not been playing well, responded with five points down the stretch.

Dandridge finished with 24 points, Wes Unseld had 17 (11 points in the third period), and 12 rebounds, Tom Henderson 24 and Ballard 14.

Chenier went into the game for the first time with 1:04 left in the first half.

He got off one shot, which was blocked, but by then San Diego had taken control of the second quarter on route to a 56-46 halftime lead.

San Diego showed hustle and deter-mination. The Clippers shot 56 percent for the half, including 66 percent in the first period.

Most of that fine marksmanship came from the guard duo of Randy Smith and Free, who control the San Diego offense usually by shooting as soon as they touch the ball.

Free and Smith scored 16 points each in the half. They mised only nine of 22 shots. That becomes even more impressive considering most of the attempts came from closer to midcourt than the foul line.

Clipper Coach Gene Shue lasted until 8:47 remaining in the second period before being ejected by Richie Powers, the NBA referee with the fastest thumb. Shue, who knew he couldn't pick up a third technical, took advantage of that rule to stay on court an extra three minutes to talk with Powers.

Dandridge had scored on a running layup and was fouled, causing Shue's temper tantrum. Dandridge wound up with a five-point play as he added the two technicals.

Those points gave the Bullets a 36-31 lead, their largest of the half, and capped a 13-2 Washington spurt to begin the quarter.

But without Henderson, who was on the bench after scoring 10 early points, the Bullet offense broke down and the gunning Clippers capitalized.

They zipped off 10 of the next 12 points to regain the lead, 41-38, with sub Sidney Wicks getting three of the baskets. Another came from Kermit Washington on a rebound.

Washington was involved in San Diego's early matchup changes. Instead of guarding Hayes, he switched to Dandridge while Swen Nater took Hayes and Nick Weatherspoon covered Unseld.

Smith and Free then dominated the half's final minutes. They combined for the final 13 points, including a foul shot by Smith resulting from a technical on Dandridge.

Even the intermission didn't cool off the Clippers. They pumped in their opening five shots of the third period and eight of their first nine.

Against that type of accuracy, Washington managed to hang on only through the rebounding of Unseld. He overpowered Weatherspoon for three rebound baskets and 11 points in the opening five minutes.

Free finished three quarters with 24, Smith 18 and Weatherspoon 16. The Clippers shot better than 60 percent for the period to take a 93-75 margin into the fourth.