The expansion is an effort of Truong Hai Corporation, as the company is officially known, to enhance its competitiveness ahead of the free flows of cars from other ASEAN countries.
Under a regional free trade agreement, tariffs on cars from the Southeast Asian bloc will be reduced to zero in 2008 from 40% at the moment.
According to the plan, Thaco will spend around 67.6% of the estimate cost building two new plants at its manufacturing base in the central province of Quang Nam, news website Saigon Times Online reported.
One of the plants will be able to churn out 100,000 units a year for Japan's automaker Mazda, one of its flagship products. Its current Mazda plant has a designed capacity of 25,000 units.
The other plant will make trucks and buses, with an annual output of 100,000 units.
Thaco also plans to expand its retail and showroom network, according to the website.
The company expected its sales to rise 40% to more than 112,000 units this year, and over VND71.73 trillion (US$3.17 billion) in revenues. It sold more than 80,400 units last year, up 90% from 2014.