The surprise shut down of the Voice of the Thai People, a radio station in southern China that six times daily broadcast the views of the Communisty Party of Thailand, has focused attention here on growing cooperation between the Thai and Chinese governments.

Calling the closure "temporary," the station went off the air without further explanation on July 11. But one theory being offered tentatively by political analysts here is that China silenced it as a gesture of support for Thailand and its posture against Vietnam.

Since 1965, the Thai Communists, with political and some material support from China, have waged an insurgency aimed at overthrowing the military-dominated governments in Bang-kok.

The "gesture of support" theory of the station's closure says China is again showing itself willing to put ideology aside to settle accounts with Vietnam and restore Chin se influence in Cambodia.

China sees Vietnam's presence in Cambodia as an extension of Soviet influence in the region. Thailand is alarmed at the wave of refugees the fighting has brought and the presence of a mechanized, hostile army only 100 miles from its capital.

These mutual concerns have led China and Thailand into an informal working relationship that has kept the remnants of the army of Pol Pot battle-ready. It is recognized that the Vietnamese are too strong to be driven from Cambodia; rather the idea is to wear them down sufficiently so that they will seek a negotiated settlement.

Thai-Chinese relations were already at a high point in December when Vietnam invaded Cambodia. Chinese senior vice premier Deng Xiaoping had just received a rousing welcome when he visited Bangkok in November.

As the Vietnamese advanced into Western Cambodia, Thailand took in large numbers of Khmer Rouge officials and Chinese advisers. A Thai military helicopter flew into Cambodia to pick up Pol Pot's foreign minister, Ieng Sary, who quickly left for China from the Bangkok airport.

Thailand continues to recognize the Pol Pot government and to allow its troops to rest in border sanctuaries and keep their arms. The Khmer Rouge also have been given passage across Thai territory to escape Vietnamese pincer attacks. (The tens of thousands of Khmers forcibly repatriated last month appear to have been predominately unarmed civilians.)

In Bangkok, the Thai supreme command keeps the Chinese Embassy closely informed of developments on the border, a Thai official said.

Many diplomats here believe the embassy is actively assisting Khmer Rouge troops in the field. Using sympathetic Thai-Chinese merchants as intermediaries, it arranges for food, medicine and other supplies to be bought in Thai border towns for the troops, Western diplomats said.

And as a Thai official noted, "You can buy arms anywhere in northeastern Thailand." The Khmer soldiers are believed to obtain small arms and ammunition from traffickers by trading gold and cash supplied by the Chinese.

For its part, the Thai government has maintained it can do little about "commercial transactions" such as these. Nor can its army be expected to forcibly disarm thousands of battle-hardened soldiers who enter Thailand intending to return to their side of the border to continue fighting, the government says.

In Peking, Chinese leaders have assured visiting Thais that China will come to their aid if Vietnam attacks, a pledge the Thais say was unsolicited, but which they seem to have welcomed.

Few analysts think a full-scale attack is likely. Vietnam does not appear to have anything to gain by pushing into Thailand, they say. Its army already is overextended and would likely run into Chinese intervention.

"What we are afraid of is spillover and hot pursuit," a Foreign Ministry spokesman said.

Seen in this context, the silencing of the "Voice of the Thai People" - its last offering on the air was a song entitled "Proceed to Expand Operational Areas" - is just another step along the road of Chinese-Thai cooperation.

The diplomatic analysts here caution that theories about the radio's demise are still very much speculative. Three arguments weigh against the cooperation theory:

The Chinese have always insisted on a distinction between government-to-government and party-to-party relations. Closing the station, which in April began to broadcast attacks on Vietnam, denies the Chinese a valuable propaganda conduit. And it could prompt the Thai Communists to turn to the Soviets or Vietnamese for help in running the radio station.

Other analysts feel that pro-Vietnamese dissent within the Thai party's own ranks might be the cause. A struggle over radio programming has erupted, they speculate, and the station has closed down until it is resolved. The major counterargument here is evidence that the split is not wide and that the pro-Chinese party members are still very much in control.

Finally, it has been suggested that the station's equipment might be being repaired, replaced or moved. Again, there is strong evidence the other way: the Malayan and Burmese Communist radio services, which are believed to use the same transmitter, are still on the air.

"I must admit I'm completely baffled," said one officer at a Western embassy here. "I can think of at least half a dozen explanations, but I haven't a clue as to which is the real one."

The station's final broadcast said the shutdown would be temporary.It is conceivable that the hour-long programs will resume anytime soon with a detailed explanation of the interruption that will make the idea that China was appeasing Thailand seem totally fanciful. However, the cooperation between the two countries that prompted that explanation continues to be real. CAPTION: Map, no caption, By Dave Cook - The Washington Post