Israel has threatened military strikes on Iranian nuclear facilities, and Iran has blamed the Jewish state for the recent killings of Iranian atomic scientists.
Iran denied responsibility for the attacks in India and Georgia, which appeared to mirror the killings of the Iranian scientists that used "sticky bombs."
The blasts in Bangkok wounded four Thai civilians and blew off the leg of an Iranian who had fled a house carrying what looked like grenades after a cache of explosives ignited there, apparently by mistake.
When police searched the house, the bomb squad found and defused two explosives, each made of three or four pounds of C-4 explosives inside a pair of radios. The national police chief, Gen. Prewpan Damapong, said the bombs were "magnetic" and could be stuck on vehicles.
The wounded Iranian was in police custody at a Bangkok hospital, and a second Iranian was arrested after he tried to board a flight for Malaysia. Security forces hunted for a third Iranian suspect.
Israel's Channel 10 TV quoted unidentified Thai authorities as saying the captured Iranians confessed to targeting Israeli interests. The site of the blast is just a few miles from the Israeli Embassy.
There was no comment from Iranian officials in Tehran on Tuesday's explosions.
Thai government spokeswoman Thitima Chaisaeng said "we need more analysis" to determine who was behind the attack and whether Iran was involved. She declined to comment on what the Iranians might have been planning or whether targets had been identified.
There seemed to be no doubt in the minds of Israeli officials, who blamed Iran and its Lebanese ally, Hezbollah.
Israeli Defense Minister Ehud Barak said in Singapore: "The attempted terrorist attack in Bangkok proves once again that Iran and its proxies continue to perpetrate terror. The recent terror attacks are yet another example of this."
Iran and Hezbollah are "unrelenting terror elements endangering the stability of the region and endangering the stability of the world," added Barak, who was in Bangkok on Sunday, according to Israel's Defense Ministry.
Israeli Public Security Minister Yitzhak Aharonovitch told Israel Radio: "We know who carried out the terror attacks, we know who sent them, and Israel will settle the score with them."
On Monday, Prime Minister Benjamin Netanyahu said Israel had thwarted attacks in recent months in Azerbaijan, Thailand, and unspecified other countries. He blamed Iran and Hezbollah.
Hezbollah battled Israel in the summer of 2006, and on Sunday, the Lebanese guerrilla group marked the anniversary of the 2008 assassination of one of its commanders, Imad Mughniyeh, in a bombing widely believed to have been carried out by Israel.