SEATTLE (AP) _ Even the fiery death of the founder of The Order failed to cool the ardor of the Nazi-like group's fugitive security chief, who tried to get members to regroup, a former member testified Tuesday.

Randall Eugene Rader, who organized a training camp and taught survival skills, said he rejected the move by Richard E. Scutari because ''I knew it wasn't possible.''

In his third day of testimony in the federal racketeering trial of 10 accused Order members, Rader, 34, of West Plains, Mo., said he was returning from a land-buying trip to Missouri when he learned that founder Robert J. Mathews had died last Dec. 8.

Mathews died in a fire that destroyed his waterfront hideout on Whidbey Island, north of Seattle, after a 37-hour standoff with the FBI.

About a week later, Rader testified, defendant Ardie McBrearty told him he had arranged for Scutari to call a pay telephone outside a supermarket in Newport, Wash.

''He told me that The Order would continue after Mr. Mathews' death and that he wanted me to have 10 men trained by June (1985).

''I changed the subject because I knew it wasn't possible - and by that point, I had radically decided that I would have nothing further to do with The Order,'' Rader said.

Scutari, a Florida man in his late 30s or early 40s, is the only one of 23 people indicted in the case who remains at large. Former Order members have described him as dangerous and highly skilled in martial arts.

Rader is the ninth former Order member or associate to testify in the trial, now in its ninth week in U.S. District Court. The 10 defendants are accused of using robbery, murder and counterfeiting in a plot to establish a white homeland without Jews, minorities or the federal government.

Rader and 10 others have pleaded guilty in the case. Another member is being held in Missouri pending trial on charges of killing a state trooper.

After talking with Scutari, Rader testified, he told Order member Ken Loff he had decided to return to Missouri.

''I told him the jig was up, ... that we were either going to jail or going on the run,'' he said.

Rader said he camped on the Missouri property for about a month before returning to Washington to move the rest of his family's belongings on March 1, the day he was arrested in Spokane.

Rader also testified that he had searched for property in Missouri or Arkansas to establish a second training camp after the Idaho camp became snowed in for the winter.

Rader also testified today that a man identified only as ''Walter'' was engaged by McBrearty to set up a nationwide computerized communication system for The Order.

Rader said McBrearty described Walter as a tax resister from Wisconsin who was on the run from authorities. McBrearty said Walter could write computer programs that would change codes automatically as messages were transmitted over telephone lines, Rader said.