The request will refer to "malicious treatment in Thailand, where they lack security and freedom", Watchara said.
Thaksin, 59, his wife Khunying Pojaman, 51, and their three children fled to London last week soon after Pojaman was convicted of tax evasion.
Thaksin issued a statement from London a day after his arrival accusing the Thai judicial system of treating him unfairly. He asked his supporters to maintain their loyalty but fell short of saying when he would return to Thailand.
The Supreme Court is trying Thaksin and Pojaman in absentia on corruption charges, accusing him of using his political influence as premier to help his wife buy a plot of prime Bangkok real estate on Ratchadaphisek Road from the central bank at a bargain price.
They each face up to 13 years in prison if convicted. Since the case is before the Supreme Court's Criminal Division of the Political Office Holders, they would have no avenue of appeal. Authorities have already frozen Bt69 billion of Thaksin's assets pending resolution of the case.
In related development, the Supreme Court yesterday issued a summons for a former defence lawyer who is serving a six-month jail term for contempt to testify as a witness in the Ratchadaphisek land case.
Presiding judge Thonglor Chomngam exercised his judicial discretion to hear the testimony of Pichit Chuenban on his involvement in defending Thaksin and Pojaman, both co-defendants and fugitives living in exile in London.
Pichit is expected to take the witness stand tomorrow. His summons was served at the remand prison where he is serving time in connection with a Bt2-million bribery attempt, ruled by the high court as contempt and interfering with the judicial proceedings on the case.
Lead defence lawyer Kamnuan Chalopatham said that following the contempt conviction, the defence had removed Pichit from the list of defence witnesses although the judge deemed it necessary to hear his testimony.
"At this juncture, I am not sure whether Pichit's statement would be in favour of the defence," he said, arguing that everything would depend on the nature of the questions posed by the presiding judge.