Challenger Victor Korchnoi took an early psychological advantage over world chess champion Anatoly Karpov in the preliminaries to their match, which begins tomorrow in the Philippine mountain resort of Baguio City.

Psychological annotators had marked Korchnoi slightly behind the champion when he lost the battle of the flags over the weekend, but he took a significant lead at the opening ceremonies yesterday when he drew the white pieces for the first game (scheduled to start today and when the Philippine Armed Forces Band blundered in its performance of the Soviet national anthem.

Korchnoi, who defected from the Soviet Union two years ago and has been a thorn in the side of the Soviet government ever since, had planned to sit down through the playing of the anthem. When the band struck up "The Internationale" instead, the broke out laughing while carefully remaining seated.

"The Internationale," a song of international working-class solidarity with dangerously deviationist sentiments, was ousted as the Soviet national anthem in 1943. Soviet dignitaries on the stages stood impassively through the performance.

Earlier, Korchnoi had been denied the right to display the Swiss flag or have the Swiss national anthem (which is identical to "God Save the Queen") played during the ceremonies. Instead, he asked for a performance of the "Ode to Joy" from Beethoven's Ninth Symphony, pointing out that in the original words it had been an "Ode to Freedom."

In the weekend battle of the flags, the Soviets had threatened to walk out on the match if Korchnoi played under the flag of Switzerland, where he is a resident but not yet a citizen. They suggested instead that he might play under a white flag with the word "Stateless" on it. In a compromise solution, representatives of the International Chess Federation decided that no flags would be shown at the table, as they usually are in international chess events.

(Flags are a recurring motif in Korchnoi' running battle with his former homeland. In a match with another Russian grandmaster last year over the same issue, he threatened to play under a skull and crossbones - after which the Russian flag was quietly removed.

Expert observers here were relucant to predict the outcome of the match - or even how long it will last. Four years ago, Karpov beat Korchnoi in a 24-game match by a score of 3 to 2 with 19 draw, but Korchnoi claims and his record indicates that his chess has improved since then. All observers expect a close match.

Losing the championship to Korchnoi "would be a catastrophe" to the Russians, said one European grandmaster who asked to have his name withheld, whereas losing to Bobby Fischer six years ago was only a "tragedy."

"To lose is always terrible," he said, "but you see, Korchnoi left Russia because he said he couldn't play good chess there. Now, if he wins, it would prove he was right - and I think it would create bad political problems in Russia."