Thailand is in the middle of a diplomatic row with the United States after its revered king was used in a spoof advert for a restaurant.

Thai Prime Minister Thaksin Shinawatra has joined top diplomats and citizens to denounce the promotion for the bar in Philadelphia, America's City of Brotherly Love.

King Bhumibol Adulyadej is considered by some Thais as a living god (AP)

The owner of Saint Jack's restaurant, Sherry Levin, has refused to withdraw the ad depicting the 74-year-old king as an urban hipster with bleached highlights and stone-encrusted glasses.

She has been besieged by phone calls from angry Thai residents and officials, but insists the drawing is harmless fun.

Thais 'disturbed'

Prime Minister Thaksin said his government had requested US authorities' help in having the advertisement withdrawn.

"I'd like to ask [the US] for co-operation for the sake of... international relations," he said.

"What the restaurant did really disturbs Thai people's feelings and that definitely isn't good."

I told them: 'Wow, you guys really have to lighten up'

Restaurant owner Sherry Levin

Thai Foreign Minister Surakiart Sathirathai said his ministry has done "everything it could".

He indicated that legal action could be taken by private individuals.

King Bhumibol Adulyadej - the ninth king of the Chakri Dynasty - is one of the most revered kings in Thailand's history for his hard work and devotion to his subjects.

Unlike in other countries, Thailand's king is deemed untouchable and Thais do not tolerate any criticism of him, either by themselves or by outsiders.

Under laws rarely applied in recent times covering defamation of the monarchy, criticism of the royal institution is punishable by up to 15 years in jail.

Unrepentant

But Ms Levin was unrepentant.

"Even while they were telling me how horrible this thing was that I did, I couldn't comprehend how it could have been that bad," she said.

"Eventually, I told them: 'Wow, you guys really have to lighten up.' It was not that disrespectful."