Thailand's king was admitted to hospital on Saturday after feeling weakness on the right side of his body, the royal palace said.
The 79-year-old King Bhumibol Adulyadej was takento Bangkok's Siriraj Hospital, where tests found a slightly inadequate blood flow to the brain, the statement said.
His condition improved after doctors administered medicine for several hours, the statement said, adding that the king would remain in the hospital for monitoring.
Bhumibol, the world's longest serving monarch, is greatly loved by Thais and regarded by some as semi-divine. Strict laws forbid any criticism of the monarchy in the country.