In March, 1966, China's then-President Liu Shao-chi took a diplomatic trip to West Asia. With him was a short, stocky, nondescript, man who Liu might have thought was protecting him. In fact, the man was measuring him for his eventful fall from power half a year later.

That fellow traveler was Wang Tung-hsing, a 61-year-old native of Kiangsi province who in the past few days has been admitted to the highest pinnacle of Chinese leadership but about whose responsibilities in the Peking government almost nothing is known for sure.Formerly he had the nominal title of director of the administrative office of the Chinese Communist Party.

Wang, 61, now serves, according to one Western expert, as "China's chief spook," the shadowy surpervisor of China's foreign esponage and extensive domestic spy network designed to prevent subversion at home.

His new prominence may derive directly from the equally murky events of last Oct. 6, when former Party Chairman Mao Tse-tung's widow and three of her close allies on the Politburo were arrested around midnight and sent off to political oblivion.

As a long-time commander of the crack 8341 unit that provides security and also some espionage service to the chairman of the Communist Party, Wang's loyalties on that night, just a month after the death of Mao, must have been subject of great concern to the factions struggling to inherit Mao's mantle.

Reports coming out of China indicate that Wang was willing to turn his back on the wife of the man he had served as orderly and bodyguard since before the Long March in 1933 and support the relatively unknown Hunan bureaucrat Hua Kuo-feng, the candidate of most of the influential party and army veterans for the chairmanship. Wang reportedly alerted Hua when Chiang attempted to remove some of Mao's papers from the office after his death, allegedly to alter them in a way that would support her own claim to the chairmanship.

After the purge of Chiang Ching and her allies, Wang allegedly was assigned to help conduct the investigation of their crimes. He seemed to be inheriting the role of Kang Sheng, the man who, until he died in 1975, was Mao's trusted confidant and informant on matters of espionage and security.

After Wang's role as Mao's personal guard ended with the Communist victory in 1949, he served in an assortment of public security ministry that he began to take on extraordinary responsibilities, being put in charge, according to one report, of detaining an army officer who was one of the first purge victims in the Cultural Revolution.

His assignment to follow Liu on his trip to West Asia seems in hindsight a clear Mao attempt to keep tabs on the man Mao considered the principal villain in his fight against an entrenched bureaucracy.

It appears that under Kang's leadership, Wang watched out for disloyalty to Mao in the Chinese army as it played a crucial role in the factional struggles of the late 1960s.