The recent small-scale incursions into Thailand of Vietnamese soldiers apparently chasing anti-Vietnamese Cambodian guerrillas illustrates one thing: For some time to come, Thailand is likely to be the pivot in a struggle for influence in Southeast Asia between Vietnam and its Soviet backers, on the one hand, and Cambodia, supported by China and the United States, on the other.
No one seriously expects a large numbers of Vietnamese soldiers to pour into Thailand. Vietnam has problems enough digesting Cambodia. Nor is a large-scale Thai action against Vietnam likely. Thailand's main problems are internal.
But one possibility is a building confrontation, even though it takes the form of minor skirmishes. Vietnam's efforts to eliminate the anti-Vietnamese Cambodian guerrillas near the border may require that from time to time Vietnamese soldiers enter Thai territory -- even in small numbers -- either accidentally or on purpose.
Thailand, as a sensitive sovereign country, can under no circumstances tolerate such insults. A recurrence of such confrontations even on a small scale could make it even more difficult for Thailand and Vietnam to improve their delicate relations.
In fact, the Thais (knowing how confident the Vietnamese are, and how arrogant they can sometimes be because of their victories over both France and the US) are sometimes easily offered by Vietnamese statements and actions that might not offend others.
The Vietnamese Army is formidable and experienced, but in western Cambodia it is hampered by its long supply lines to Vietnam. Any full-scale invasion of Thailand would therefore be most difficult.
Thailand for its part has a strong, well- trained, effective Army. Foreign aid has strengthened this Army, and special American training has improved these elite units.
The more interesting long-term questions raised by recent events in Thailand are internal ones. The main fomentor of insurgent activity in the country is the Thailand Communist Party, which is largely pro-Chinese. The party has been backed by the Chinese, and one hope of the Thai government was that if relations with China improved, as they have done, China's support of these insurgents would diminish.
The danger now, though, is that Vietnam might fill the vacuum left by China and begin to support a Thai communist insurgency. Such an insurgency could exploit the many social and economic grievances harbored by poor Thais, especially those in the countryside of the northeast.
If this should happen over a number of years, Thailand could face an indirect but serious threat from Vietnam. On the other hand, many Thais are strongly anti-Vietnamese. They dislike, if not hate, the Vietnamese as a people.
This attitude is very different from their more positive attitude toward the Chinese. In the long run, disaffected Thais may prove even more reluctant to lend their support to a Vietnamese-backed insurgency than to a Chinese-supported movement.