Doctors performed a procedure known as balloon surgery to widen the arteries on Tuesday after tests had shown insufficient blood in the heart muscles, the statement said.
In the past month, the king has also been treated for a build up of fluid surrounding the brain and a swollen lung.
An X-ray on Saturday showed less fluid around the brain, the statement said.
The monarch's health is closely watched in Thailand as he is seen as a unifying symbol and pillar of stability in a society that has suffered increased political divisions and violence.