It was not immediately possible to reconcile the different death tolls.
The security post targeted in the bombing is on a road connecting Thal with Miran Shah, the main town of North Waziristan tribal area.
Violence has increased in Thal since anti-government fighters in the region renounced a peace deal with the authorities last month.
For the last 10 months, the area has been in a state of high tension. In the past month alone, nearly 200 people, mostly policemen and army troops, have lost their lives.
Ahmed Barakat, Al Jazeera's correspondent in Pakistan, said the bomber drove his explosives-laden car into a military checkpost just as solders were gathering at the spot.
The death toll is likely to rise considering the serious condition of some of the wounded soldiers.
Barakat also said that the Pakistani police had foiled a "suicide" operation in Khoza Kheila district and arrested the would-be bomber.
In other attacks on Monday, fighters fired three rockets at a base housing army and paramilitary troops in the North Waziristan town of Mir Ali, a security official said.
Two rockets landed in a field near the base and one struck a soldier's residence inside, injuring a woman, the official said.
Pakistani soldiers returned fire but it was not known whether the attackers suffered any casualties, he said.
And in Tank, a town south of North Waziristan, fighters detonated a bomb near a military convoy, but no one was hurt, Arshad said.
On Sunday, army helicopter gunships struck suspected fighter hideouts near Mir Ali, killing 15 fighters.