"At least 31 people, including regime troops, were killed when a man detonated a truck laden with explosives at a checkpoint near an agricultural vehicles company on the road linking Hama to Salamiyeh," the Syrian Observatory for Human Rights said.
The Britain-based watchdog said the death toll was likely to rise, as "there are dozens of wounded, some of them in critical condition".
State television had earlier reported multiple casualties from a bombing in Hama without giving a more precise casualty toll.
But in late summer of that year, security forces stormed the city, killing scores of people. They have held a tight grip on the city ever since.
While several other Syrian cities have been engulfed by fighting, Hama has seen only sporadic violence in recent months.
However, the surrounding province has seen some major clashes between troops and rebels.