Thai 100 percent grade B was down $4 at $285 a tonne free on board on Thursday from a week earlier.
The domestic price of 100 percent grade was down 100 baht at 11,100 baht a tonne ($272) from last week's 11,200 baht.
"Trade is generally quiet. Only some small business of parboiled grade has been done," said one trader.
"Some buyers have yet to cover their positions for December shipment, but, if they want to cover, they will buy from Pakistan or India where prices are cheaper."
Thai 25 percent broken grade is $35 a tonne free on board more expensive than rice of the same grade from Pakistan.
More supply is expected to arrive on the market in coming weeks as the harvest for Thailand's main crop has started, traders said.
The government estimates the new crop could grow 14 percent from last year to 21.27 million tonnes of paddy due to good weather and good domestic prices.
Traders said they did not expect the government to release its stock in coming weeks because it was concerned that would depress domestic prices.
"I don't think the government will take any further decision on the stock. It will not help the farmer by selling it now because it will depress the price."
Thailand, the world's largest rice exporter is still holding around 1.7 million tonnes of rice, which includes more than 1 million tonnes of Jasmine grade.
Between January 1 and October 28, Thailand exported six million tonnes, 27 percent less than the 8.23 million tonnes shipped in the same period last year.