Pichit Chuenban, the chief of Thaksin's legal defence team, confirmed that his client was "poised to return" from abroad where he was at the time of the military coup in September last year.
He said Thaksin will surrender to police when he arrives and is expected to seek his release on bail.
Last week, authorities returned Thaksin's diplomatic passport, paving the way for his return to face charges of corruption, abuse of power and of concealing assets.
Both he and his wife, Pojaman, are also facing charges of conflict of interest in connection with her 2003 purchase of prime Bangkok property from a state agency.
Rakkiat Wattapong, the supreme court secretary general, had earlier said that Thaksin would be detained when he arrives in Thailand.
Thaksin had expressed his plans to return after his allies in the People Power Party won the December elections and formed a new coalition government.
Opposed to interference
The People's Alliance for Democracy (PAD), which led months of demonstrations demanding Thaksin's resignation before the coup, vowed to stop any attempt to clear him of corruption charges.
Suriyasai Takasila, the group's spokesman, said PAD will fight any judicial interference by the new government in Thaksin's case.
"PAD is warning this government the political crisis will be worse than in 2006 if it continues to whitewash the charges against Thaksin," he said.
"Thousands will take to the streets again if Thaksin returns and does not face trial in court in accordance with the law."
Following the coup, a court order disbanded Thaksin's Thai Rak Thai party, and barred him and 110 executive members from holding public office for five years.