Thaksin Shinawatra, the ousted Prime Minister of Thailand and opposition leader in exile, has called for reform of the country’s revered monarchy and spoken of a “shining” new age after the era of the ailing King, Bhumibol Adulyadej.

Mr Thaksin’s remarks, which touch on taboo areas of Thai politics, come as he prepares to return to South-East Asia from exile in a move which has caused turmoil in Bangkok. He plans to arrive in Cambodia, Thailand’s neighbour, tomorrow, on a visit which has caused an intense row between the countries.

The appointment of Mr Thaksin as an “adviser” by Hun Sen, the Cambodian Prime Minister, has angered and humil-iated Abhisit Vejjajiva, the Thai Prime Minister, and raised suspicions that Mr Thaksin is plotting a political comeback from a base in Cambodia.

The two countries have withdrawn their ambassadors and there are fears of military skirmishes along the disputed border, following clashes last year.

Mr Thaksin’s remarks about the monarchy are further evidence that, three years after being forced out as democratically elected Prime Minister in a military coup, he is still contemplating a political future in Thailand. His remarks also suggest that he is placing hope in the man likely to accede to the throne, Maha Vajiralongkorn, the Crown Prince.

“He’s not the King yet. He may not be shining [now],” Mr Thaksin told The Times in an interview from his exile in the Arabian Gulf city of Dubai. “But after he becomes the King I’m confident he can be shining ... it’s not his time yet. But when the time comes I think he will be able to perform.”

Mr Thaksin was the most popular — and the most divisive — Prime Minister in his country’s recent history. Since the coup in 2006 Thailand has been torn by frequently violent demonstrations by his “Red Shirt” supporters and the “Yellow Shirts” who oppose him in the name of King Bhumibol.

The King has not explicitly endorsed their movement but many of Mr Thaksin’s supporters believe the coup could not have happened without his consent.

Mr Thaksin is careful to emphasise deep loyalty to King Bhumibol but is deeply critical of the “palace circle”; principally, members of the Privy Council. He blames them, along with senior generals, for the coup. King Bhumibol quickly accepted the coup and has ignored a petition signed by 3.5 million Thais to pardon Mr Thaksin. However, the King has been in hospital for seven weeks, reportedly suffering from pneumonia, and Thais are looking ahead with trepidation to life after his reign.

Prince Vajiralongkorn is the King’s designated heir but is unpopular with many Thais because of rumours about his private life. Supporters of Mr Thaksin have told The Times that by endorsing the Crown Prince and lending some of his own personal popularity he hopes to gain the support of a future monarch who will not interfere with his political ambitions. “The Crown Prince may not be as popular as His Majesty the King,” Mr Thaksin told The Times. “However, he will have fewer problems because the palace circle will be smaller . . . He had education abroad and he’s young — I think he understands the modern world.”

Mr Thaksin, who was sentenced in absentia to two years in jail for corruption, insists he does not intend to settle in Cambodia — but even his temporary presence there, close to Thailand’s northeast, where he enjoys passionate support, is deeply discomforting for Mr Abhisit.

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