SAIGON — Santa Claus was denied entry to South Vietnam here Sunday, perhaps because he chose to ride a plane into a commercial airport rather than land a sleigh at a remote fire support base.

When Santa deplaned at Tan Son Nhut he had to go through the customs and immigration lines just like everyone else, despite his flowing white hair and beard and the red velvet draped over his ample frame. But unlike most of the others going through the line, Santa had no visa.

"No visa, no entry," Vietnamese customs officials said.

"There's no clemency, even for Santa, said a Pan American World Airways official in the small immigration office that was rapidly becoming overcrowded with policemen, airline representatives, Santa, his helpers, military escorts, and sight seers.

Santa was actually Jim Straughan, a Pan Am mechanic from Miami, Fla. He had come to Vietnam to pass out Christmas goodies to patients in U.S. field hospitals and Vietnamese orphanages. Two other Pan Am employees, Rice McGuire and Norm Fisher, accompanied him from Miami.

Straughan said this was his third trip to Vietnam and the entry problems this year arose from a misunderstanding about visa requirements. He said last year his party had been able to get seven-day visas when they arrived because they were traveling on company business.

They thought the procedures would be the same this year but the rules had been changed to require a visa before arriving.

As telephone pleadings with the South Vietnamese vice-consul and American military officials failed to produce Santa a way into the country, he scratched his beard, patted his stomach and offered a last desperate ploy. "We'll even enlist. Have you got someone to swear us in?"

Even that failed. Santa and his party flew out of Saigon an hour after they landed. They were on their way to Manila where they hoped to get visas and be back in Saigon by Monday afternoon.