Fighting in western Kampuchea (Cambodia) is testing Thailand's defense against Vietnamese attack.
The question is whether the current Vietnamese dry-season offensive against guerrillas will spill across the border into Thailand.
Already more than 3,000 Kampuchean refugees have sought shelter in Thailand from the latest fighting. Thai border units used warning artillery fire to block two attempts by a Vietnamese company to cross the border in pursuit of refugees, according to a Thai military command spokesman.
Thailand has long been concerned that Vietnamese forces, which invaded Kampuchea in early 1979, might be tempted to strike into Thailand in hot pursuit of guerrillas opposing the Vietnamese-backed government in Phnom Penh. In June 1980 Vietnamese forces did briefly intrude on Thai territory and withdrew after sharp fighting.
This time Thai authorities see little likelihood of so serious an incursion, according to a Western source with access to Thai thinking. Vietnam has stepped up the level of fighting in western Kampuchea, but not as high as it could.
Vietnam is considered unlikely to launch any major incursion, remembering, as it does, how well the Thais fought in 1980. Another deterrent is the likelihood that China would retaliate in support of Thailand with an invasion on Vietnam's northern border.
Vietnam usually raises the level of fighting in Kampuchea during the dry season, when its troops can move about more easily with the help of tanks and trucks.
This time, for the first time, Vietnam is reported to be using planes in its battle against some 35,000 communist Khmer Rouge guerrillas armed and supplied by China. Military actions by the Khmer Rouge, as well as by anticommunist anti-Vietnam guerrillas, are also reported up.
The offensive by Vietnamese and Phnom Penh government troops has also hit northern Kampuchea, in the area adjoining Laos and Thailand. But the current border problem relates to Vietnam's activity in the area of Poipet, staging point for operations into the Khmer Rouge mountain stronghold of Phnom Milai. Fresh Vietnamese troops are reported to have moved into the area. New equipment, including T54 and light amphibious PT76, tanks and a variety of long range artillery is also said to be in the area.