In ancient times, why not go to Southeast Asia, where there are endless grains and fruits?

Ancient dynasties explored Southeast Asia.

However, due to the low level of productivity and technology in ancient times, the problems of geography, climate and logistics in Southeast Asia could not be overcome in ancient times.

Often, the Central Plains troops will die halfway in Southeast Asia, such as the epidemic of miasma and plague, and the logistics supply is intermittent because of the difficult journey of the tropical rain forest. Therefore, the fighting is very unfavorable.

Therefore, when the Central Plains Dynasty was strong, it could only control the land through "remote control", but it could not achieve comprehensive and direct rule like the mainland.

Later, the civilization of Southeast Asians developed from primitive tribes to feudal dynasties. It is even more difficult to develop here, because we already have the strength to compete with the Central Plains Dynasty. Even some territories in Southeast Asia have been eroded by it.