Rep. Lee Cheol-woo of the ruling Liberty Korea Party told reporters about a report from the National Intelligence Service (NIS) briefing the parliamentary intelligence committee on the Sunday testing.
The DPRK test-launched an intermediate-range Pukguksong-2 ballistic missile towards its eastern waters that flew about 500 km.
Lee was quoted by local media outlets as saying that it could have flown over 2,000 km if it was fired at a normal angle. The Sunday launch was conducted at an angle of 89 degrees, said the parliamentary committee head.
The DPRK's KCNA News Agency said the high-angle testing was aimed for the security of neighboring countries.
According to the NIS analysis, the missile traveled at a speed of Mach 8.5, lower than the South Korean military's estimate at over Mach 10.
It could be a deliberate underestimate as Terminal High Altitude Area Defense (THAAD) interceptors are incapable of shooting down incoming missiles at a speed of over Mach 10.
Seoul and Washington agreed in July last year to deploy one THAAD battery in southeast South Korea by the end of this year.
It caused strong oppositions from China and Russia as its X-band radar can peer deep into territories of the two nations. The deployment means South Korea becoming a part of the global missile defense system of the U.S. to contain China.
At home, parliamentary and public objections remain strong as doubts were cast about the THAAD's capability to protect against the DPRK's nuclear and missile threats.
Most of DPRK missiles targeting South Korea fly at an altitude of less than 40 km. THAAD is designed to intercept missiles at an altitude of 40-150 km.