Nukul Bawornsirinukul, chief of the 18,000-member union, said that TOT had been deprived of Bt31.8 billion in revenue since 2003, due to the move.

The Supreme Administrative Court will decide whether to prosecute the case.

The union filed a similar case with the Central Administrative Court on December 28. At the time, Nukul filed the case as an employee of TOT and named the Finance Ministry as the defendant.

He said then that the loss of this income caused a drop in remuneration to TOT employees. In the filing, he said he was entitled to an additional bonus payment of Bt320,000.

The lower court has not yet announced if it will proceed with the case.

The previous government passed the telecom excise resolution on February 11, 2003. It has permitted private operators to deduct part of their concession fee as excise tax.

Under the excise tax, private cellular concessionaires have directly paid 10 per cent out of their concession fees as excise tax to the government before sharing the remainder with their state concession owners TOT or CAT Telecom.

The fixed-telephone operators have paid 2 per cent of their concession fee as the excise tax to the government before giving the remainder to TOT.

The resolution prompted a drop in the concession revenues to TOT and CAT, while both must pay excise taxes like their concessionaires.

According to the Information and Communications Technology Ministry, TOT and CAT lost Bt23.903 billion and Bt15.249 billion respectively during 2003 and 2005 due to the resolution.

The ministry will propose a plan to the current government this month to terminate the resolution. If the Cabinet approves the proposal, all private telecom concessionaires will resume paying the full concession fee to TOT or CAT and paying the additional excise to the government.