The Supreme Administrative Court is likely to rule this month on a controversial case involving a Cabinet resolution on April 7, which allowed Prime Minister Thaksin Shinawatra to take indefinite leave from office and appointed Chidchai Vanasatidya, the deputy prime minister, to take over his role.

"We have heard that the court might decide on this issue on either May 25 or 29," said one legal source.

The Supreme Administrative Court's ruling will have far-reaching political implications, as it will directly affect the entire legal status of Thaksin and his Cabinet.

Earlier this week the Law Society of Thailand filed a case to the Supreme Administrative Court charging that the Cabinet had illegally allowed Thaksin to take leave of office, although he was still caretaker prime minister.

While Thaksin has made known his intention not to perform any official duty and has been absent from Government House, he still receives a salary and all benefits as a public office holder.

The Law Society of Thailand would like Thaksin to return his salary and benefits to the state coffers and has asked the court to revoke Chidchai's role as caretaker premier on his behalf.

This legal question is emerging as an explosive political situation as Thaksin and his Cabinet could lose their status as result of the ruling.

On April 4, Thaksin announced on television that he would not take over the premiership during the formation of a new Cabinet until the political reform process is completed.

On April 7, the Office of the Secretary of the Cabinet issued a circular to announce that the prime minister would like to take leave. In that circular, Thaksin told the Cabinet that after working for five years without rest, he would like to take leave from his duties until the new Cabinet is formed.

He also said he would like to restore unity to the country.

The Cabinet approved the appointment of Chidchai as caretaker prime minister running the executive branch on behalf of Thaksin.

Thaksin also had his personal belongings removed from his office at Government House.

Since April 7, he has not attended any Cabinet meeting. He also told reporters he was unemployed and not involved in any affairs of the state.

"The implication of the Cabinet's resolution is that Thaksin has made known his intention both legally and practically to resign as caretaker prime minister," said one constitutional expert. "If the court rules along this line, Thaksin will lose his caretaker premiership status. And as a result, the entire Cabinet will also lose its status."

"It is a case of a careless blunder," he said.

Legal experts said Thaksin's taking leave of office indefinitely was not supported by any law or government regulations, for during this period he was seen playing golf during official hours and going shopping with his family.

The Cabinet's resolution for Thaksin to take leave of office and still enjoy the salaries and benefits of a prime minister is illegal, they said.

Another point of contention is whether it is legal for the Cabinet to appoint Chidchai to assume the role of caretaker PM. The law only permits the appointment of someone to perform the duty on behalf of the prime minister in the event that the premier cannot perform his duty either because he is either ill or absent.

But the fact is Thaksin has been around most of this period and is not sick at all. On this basis, legal experts say that the appointment of Chidchai and other deputy prime ministers to perform Thaksin's duties might be judged illegal.