While businesses have been fawning over China, six hundred million people throughout Southeast Asia have also been getting richer, and U.S. automakers are beginning to take notice.

“Incomes are now at that sweet spot of just passing $4,000 per capita, and that’s when demand for cars just takes off,” says Michael Dunne, author of American Wheels, Chinese Roads.

Indonesia and Thailand are the fastest growing markets in the region this year.

“It will be a growth market and it can be highly lucrative for automakers,” says Dunne.

Most of the cars you see on Southeast Asian roads are made in Japan, but GM’s China President Bob Socia hinted to Reuters that he plans to change that. He’s eying a possible partnership with GM’s Chinese partner SAIC to assemble low-cost cars for the region.

It may seem like an economic no-brainer, but GM’s partnership with SAIC to sell cars in India has fallen on tough times — sales there fell 21 percent the first half of this fiscal year.