The ex-royal couple along with their grandchildren Purnika, Kritika and Hridayendra, left for Bangkok where Paras has been admitted in the Samitivej Hospital.
42-year-old flamboyant ex-prince was admitted to the hospital on February 20.
"We should believe in god and have faith on the skills of the doctors involved in the treatment," Shah told reporters at Tribhuvan International Airport.
With no significant change in his medical condition, Paras has been kept on the ventilator life support since he blacked out.
The hospital yesterday said that no significant changes were observed in Shah?s medical condition and he is still in a very critical state.
Nepal Army's Dr Kishore Rana is also accompanying the royalty, the Himalayan Times newspaper reported.
After consulting the doctors, the royal family will decide whether to shift Paras from the hospital to other facility or bring foreign doctors to assist in the treatment, newspaper reported.
Paras's wife Himani, sister Prerana and other relatives are already in Bangkok with Paras.
Paras was earlier admitted to the Norvic International Hospital in Kathmandu in September 2007 after he suffered a mild heart attack.
Kathmandu: Nepal's former King Gyanendra Shah and queen Komal Wednesday left for Bangkok to see their ailing son ex-crown prince Paras, who is lying in coma following a major heart attack last week.
First Published: Wednesday, February 27, 2013, 20:31