The monarch has had frequent bouts of ill health in recent years.
He is seen as a pillar of stability in Thailand which saw political strife culminating in last year`s coup.
Though the king has no formal political role, he is seen by Thais as a symbol of unity, having ruled since 1946, and his health is closely watched.
Last October he had his gallbladder removed. He was in Bangkok`s Siriraj Hospital for seven months, and was discharged in May this year, only to return to the hospital a few weeks later for medical tests.
More about:
