Up until October, Vietnam's car imports from the neighboring country was still ranked third but Thailand sped up in the race to the top last month.
In comparison, the Republic of Korea exported 23,232 cars to Vietnam during the period and China, 22,496 cars.
The market shift came as Thailand was boosting its auto exports amid falling domestic sales. Vietnam has become one of its key markets given tariff cuts the country is obliged to apply under an ASEAN agreement, local analysts were quoted as saying in news website VnExpress.
Since 2012, Vietnamese government has reduced tariffs on cars imported from regional countries to 50 percent. It is expected to cut the tax rate further until ASEAN cars become tax-free in 2018.
Another advantage of Thai cars is that they are much cheaper compared to those imported from China and the Republic of Korea, analysts said.
That explains why, in terms of value, Thailand auto imports remain small.
The value of cars imported from Thailand was estimated at US$406.2 million in the first 11 months, compared to China's US$869.58 million and the Republic of Korea's US$511.85 million.