Why didn't Vietnam invade Thailand when it occupied Cambodia?

I have read the relevant materials. After Vietnam invaded Cambodia, it made territorial claims to Thailand and had an armed conflict with Thailand. Hehe, although there are shemale in Thailand, Muay Thai is also very fierce. It beat up Vietnam at the border and Vietnam retreated. Then China fought back against Vietnam. In the final analysis, Vietnam can't fight well, and Cambodia can fight well. Close to the people's militia, far from the regular army of Thailand and China. Besides, Cambodia is actually supported by Vietnam, and pol pot is so autocratic that the Cambodian people will be happy as long as someone overthrows it. At that time, many Cambodians ran to the occupied areas of Vietnam and saw that Vietnam was a liberator, so it was easy to fight. But Thailand can't. Although it was an imperial system, those years were also political harmony. The country is stable. Of course not.