According to the Asean Automotive Federation, last year Thailand was the regional leader in every aspect of the industry: production, domestic sales and exports. It produced 2.46 million vehicles, while Indonesia turned out 1.2 million.
"Indonesia is expected to become Thailand's arch rival once the Asean Economic Community is integrated in late 2015," said Ong-arj Pongkijworasin, chairman of the automotive industry club of the Federation of Thai Industries (FTI).
"Indonesia's government has a roadmap to produce 4.18 million vehicles by 2025."
Mr Ong-arj was speaking yesterday at a seminar hosted by the Thai Automotive Journalists Association at the Bangkok International Trade & Exhibition Centre.
Car production in Asean's five manufacturing countries — Indonesia, Malaysia, the Philippines, Thailand and Vietnam — amounted to 4.43 million vehicles last year, up by 5% from 4.23 million in 2012.
Car sales in Asean totalled 3.54 million, a rise of 2% from 3.47 million in 2012.
Thailand sold 1.33 million vehicles last year, down 7%, while Indonesia sold 1.22 million, up 10%.
"Indonesia has been trying to develop its vehicles in a similar way to Thailand, be they eco-cars, which are called low-cost green cars, multipurpose vehicles, sport-utility vehicles, small sedans, trucks or hybrid vehicles," Mr Ong-arj said.
"More importantly, several multipurpose vehicles in the Thai market are also imported from Indonesia."
According to Mr Ong-arj, Indonesia is expected to produce 1.61 million vehicles by 2015 and 2.60 million by 2016.
However, Indonesia has cut its production forecast this year to 1.3 million vehicles from 1.4 million due to slowing demand in the country.
"The automotive industry of Indonesia has had a compound average annual growth rate of 15% since 2010, while Thailand has had only 10%," said Mr Ong-arj.
At present, Thailand has 18 car makers with a maximum production capacity of 2.85 million vehicles, while it has a supply chain of auto parts makers of more than 2,300.
Last month, the FTI cut its 2014 forecast for Thailand's automotive output from 2.4 million vehicles to 2.2 million. It also cut its estimate of domestic sales to 1 million from 1.2 million, while exports stand firm at 1.2 million vehicles.
It forecasts pickup truck sales will contribute 55-58% of domestic sales against 44.2% in 2013, while passenger cars are expected to drop to about 40% from 47.4% last year.
The passenger car market has normalised after demand was absorbed by the former government's first-time car buyer scheme.
The FTI is today due to announce car sales and production figures for July.