"We are considering taking legal action against the website," said Vissanu Meeyo, a spokesman for the information ministry. Thailand plans to sue YouTube, owned by Google, over charges of lese majeste -- insulting the monarchy, a serious crime here that carries up to 15 years in prison, the spokesman said.
The government, which came to power after a September coup, has continued to block YouTube since the first clip showing the king next to a photograph of feet, considered deeply offensive here, appeared in April.
The YouTube ban came a week after a Thai court jailed a Swiss man for 10 years for insulting the monarch by vandalising his portraits.
But the king later pardoned the man, who was then deported from Thailand.
Since the first clip, more new videos mocking the king have appeared on YouTube, including pictures of the monarch that had been digitally altered to make him resemble a monkey.
Thailand's 79-year-old king, almost universally adored by Thais, is the world's longest-reigning monarch, and one of the few who is still protected by tough laws that prohibit any insult against the royal family.