Police seized more than 4000kg of urea fertilizer and several gallons of liquid ammonium nitrate at the warehouse in Samut Sakhon, on the western outskirts of Bangkok, according to police and media reports.
The US Embassy had issued an "emergency message" on Friday warning of a possible terror threat against Americans in Bangkok, and Israel warned its citizens as well. A dozen other embassies have since urged their citizens to exercise caution.
The warnings come during heightened tension over US and Israeli responses to the prospect that Iran is moving ahead with its nuclear programme.
Thai authorities were caught off-guard by the US announcement, hastily revealing they had detained a Swedish national of Lebanese origin with alleged links to pro-Iranian Hezbollah militants and that intelligence indicated a plot could be carried out between January 13 and 15.
The defence minister said the news was not released earlier to avoid panic that could hurt Thailand's tourism industry, one of the country's biggest revenue earners.
Damage control continued on Monday, with the prime minister calling for calm.
"I'd like to tell people not to panic. The situation is under control. There is no problem," Prime Minister Yingluck Shinawatra told reporters, adding that security was increased and intelligence agencies were closely following the situation. "We can assure the safety of the (Thai) people and foreign tourists."
Details of the alleged plot remained hazy due to conflicting accounts from Thai officials, some of whom said that Thailand appeared to have been a staging ground but not the target of any attack.
"I think Thailand is likely a transit point for other regions of the world," national police chief Gen. Prewpan Dhamapong told reporters after the raid. "It is unlikely that they would have staged terror attacks in Thailand."
The US Embassy stood by its warning and said it was still in effect yesterday.
"Whenever we have specific, credible, not-counterable threats, it is our responsibility to inform Americans in Thailand," said embassy spokesman Walter Braunohler. "That's what we did Friday. We issued an emergency message, and that remains in effect."
Police were led to the warehouse by the suspect, identified as Atris Hussein. Hussein told police that he and other accomplices had rented the warehouse a year ago, according to a police official who spoke on condition of anonymity because he was not authorized to speak to the media.
The official said that police also found shipping containers, leading them to believe the materials were destined for shipment elsewhere, though he declined to say where.
Hussein was charged with illegally possessing explosive materials and faces up to five years in prison.
In Stockholm, Swedish Foreign Ministry spokeswoman Linn Duvhammar confirmed the detained suspect has dual citizenship and said the Swedish embassy is helping him find a lawyer. He moved to Sweden in 1991 and spent 2006-09 in his native country before returning.
Duvhammar said he was carrying a valid Swedish passport when he was arrested, as well as an old one that had been stained.
Police were still looking for another Lebanese suspect.
Thailand has rarely been a target for foreign terrorists, although a domestic Muslim insurgency in the country's south has involved bombings of civilian targets.
