Answer:
- Their climate
- Their culture/tradition
- Most of them were target of European Colonies.
Step-by-step explanation:
- Climate
Southeast Asian countries are located near the equator line. This make their average temperature typically higher compared to the countries on North America.
- Their culture/tradition
You can find similarities SouthEast Asian culture as if they're once originated from the same source. You can see these similarities in their traditional food, clothing's, some part of their language, etc.
- Most of them were target of European Colonies.
With the exception of Thailand, South East Asian countries were once Colonized by European Empires. Their region were targeted because they possess large amount of natural resources that can be used by European countries for their products.