Thai police have deactivated explosives hidden in a car near the residence of Prime Minister Thaksin Shinawatra.
Thailand is gearing up for an election re-run
Police said bomb-making ingredients were found in the boot of a car belonging to an army officer, who has since been detained.
Police chased the car after it was seen driving up and down near Mr Thaksin's home, reports said.
The incident came on the day that campaigning for the general election re-run kicked off.
Tensions have been high amid ongoing political uncertainty following an annulled poll in April.
Mr Thaksin's security team said that they had received a tip-off about a potential threat.
"We have had information for several months that there will be a car bomb," a representative for the security team told French news agency AFP.
Police said different kinds of explosives had been found in the car.
"We found TNT weighing five pounds, 10 bags of fertilizer mix with gasoline and three sticks of C-4 explosives," Police Colonel Sathorn Saisomboon told AFP.
The detained man, Lieutenant Thawatchai Klinchana, was being questioned, police said.
Security around the prime minister has been tight in the run-up to the 15 October polls.
The courts annulled the general election held in April after the main opposition party boycotted it, leaving Mr Thaksin's Thai Rak Thai as the only major party standing.
Thais are hoping fresh polls will end months of political turmoil, but a number of unresolved issues remain.
There is no election commission in place to organise the polls, because of the five officials, one died, one stepped down and three were jailed in July for their mishandling of the election.
Mr Thaksin has not confirmed whether he is looking to become prime minister in a new government, if the ruling party wins.