Mr Viraphol said the drop in imports was the result of lower fuel consumption.
Of the total amount, crude oil accounted for 735,000 barrels per day, down 7.7% from August, worth 78.34 billion baht. The country also imported 83,000 barrels of refined petrol per day, down 2.1%, at a cost of 6.83 billion baht.
The import of liquefied petroleum gas (LPG) was at 181,039 tonnes in September, up 0.4% from August, for a total value of 5.83 billion baht.
Thailand has capped the LPG price for many decades. The main use in the past was for home cooking, and then the majority of Bangkok taxis were converted. Since 2008 LPG has increasingly been popular among general motorists as the global oil price rose to US$140 per barrel. Since then Thailand has became a net LPG importer rather than a major regional exporter. Now the country can supply only 75% of the domestic LPG demand, with imports accounting for the rest.
For the first nine months of 2012, the average importation of crude oil and petrol was 936,000 barrels per day, with a total value of 905.56 billion baht.
During the third quarter, imports of LPG averaged 148,812 tonnes per month while total imported value for the period was 41.3 billion baht.
Meanwhile, the Nikkei business daily reported that Japanese auto maker Nissan is aiming to double its production in Thailand with plans for a new 30 billion yen ($376 million) factory near Bangkok.
The new facility in Samut Prakan province will be built near an existing Nissan plant which emerged largely unscathed from the record flooding last year that dented Japanese firms' production in the country.
Nissan's existing plant temporarily stopped production during the disaster, however, owing to a parts shortage.
The new factory, scheduled to open in 2014, will produce about 100,000 vehicles annually with plans to boost that figure to 200,000, roughly equivalent to Nissan's current annual production in Thailand, the Nikkei said.
A Tokyo-based Nissan spokeswoman declined to comment, saying only that the firm would "soon make an announcement about its business in Thailand".
In its latest fiscal year through March, Nissan made about 190,000 vehicles in Thailand, she said.
The firm has set a goal to more than double its share of the Thai vehicle market to 15 percent by fiscal 2016, the report said.
The move comes as Japanese automakers have cut production in China owing to a sales slump stoked by tensions between Beijing and Tokyo over a group of islands in the East China Sea.