the answer is: For the most part, colonies were taken by use of local rivalries, modern armies, and technology. Many of the natives resented the westerners and fought against them.
South East Asia had a large number of natural resources and population. This made industrialized European (such as England, Spain, Netherlands, and Portuguese) fought over control on the southeast Asian territories by utilizing their military powers.
The natives were forced to work as labor force with very little pay, and many of them died during the effort to regain back their independence. This is why Many of the natives resented the westerners and fought against them.