Atris Hussein, 48, was arrested in Bangkok in January last year and police later found chemicals that can be used to make a bomb at an address he rented.
According to the charges, Hussein and some unidentified accomplices had packed more than six tonnes of ammonium nitrate into bags.
In March Thai authorities alleged Atris had connections to Hezbollah, a Lebanese Shiite Muslim group that is blacklisted as a terrorist organization by Washington.
Giving testimony for the first time Atris – who was handed Swedish citizenship after claiming asylum – denied the charges and links to Hezbollah.
“I know Hezbollah in general,” he told a court.
“But I don’t have any relation – either directly or indirectly – with the group,” he said, adding the movement is widely known in Lebanon and is part of the government.
Ammonium nitrate is commonly used in agriculture, but mixed with other substances can make a bomb. Its possession requires a permit in Thailand.
Prior to his arrest, the United States had warned of a “serious” threat of a terrorist attack on tourist areas in Bangkok.
Two Iranians are currently on trial for suspected involvement in a botched bomb plot against Israeli diplomats in Bangkok in February 2012.