Bhumibol also described Surayud as "strong and careful, and a man of principle", in sharp contrast with previous birthday speeches where he reprimanded Thaksin for failing to handle criticisms or admit his mistakes.
"The prime minister is a strong man. I have to compliment him for taking the job at a time of trouble."
He said the interim government, comprising several members who were called out of retirement, was old and wise and less prone to greed.
"Old people when they take important positions, don't want anything for their personal gain. They are not greedy," said the king, who celebrated 60 years on the throne last June.
The coup enjoyed support from many citizens in Bangkok as well as endorsement from the world's longest-reigning monarch.
|The king implicitly criticised Thaksin, right, |
for being greedy and inexperienced
Elections are scheduled for October.
The king's 40-minute address was televised nationwide on the eve of his 79th birthday which falls on Tuesday.
More than 20,000 citizens sought his audience at Chitralada palace, where he delivered his speech to the interim government and dignitaries.
Former business tycoon Thaksin, 57, has been accused of enriching himself and his cronies through corrupt policies.
The king had openly opposed many of Thaksin's policies and numerous lawsuits he had filed to silence his critics.
Many also believe the deposed prime minister had exacerbated the violence in southern Thailand by using the military to confront a Muslim uprising.
On Tuesday, a bomb killed two men and wounded 18 people at a market in Yala, police said.
Four of the wounded were in serious condition.
Police said video from a closed-circuit camera showed four youths had hidden the bomb next to a food stall before fleeing the scene on motorcycles.