The announcement comes as Thailan's military-installed government announced it had cancelled Thaksin’s diplomatic passport.
Thaksin dominated Thai politics for five years, winning two landslide elections before street protests against him over corruption allegations led to political deadlock.
The coup leaders have said repeatedly they do not want Thaksin to return home any time soon, fearing that his presence may bring his supporters on to the streets.
But Noppadon said Thaksin, who won elections on the back of massive rural support but was accused by the military of rampant corruption, would not return home soon.
"His return must not be a cause for unrest," Noppadon said.
The announcement came as a foreign ministry spokesman said the government had cancelled diplomatic passports issued to Thaksin and his wife.
Kiattikhun Chartprasert, a ministry spokesman, said the decision was because of "changing political circumstances and security information".
"We have considered the changing situation with regard to national security before we came to this decision," he said.
Meanwhile on Wednesday, Thaksin's son, Phantongtae Shinawatra, 27, gave testimony before investigators as part of a probe into millions of dollars in unpaid taxes from the sale of the family's telecommunications empire last year.
The Assets Examination Committee ruled last month that two of Thaksin's children owed 5.8 billion baht ($163m) in taxes from the sale of Shin Corp last January.
Thaksin's daughter, Pintongta, is scheduled to testify on Friday.
Based on the closed-door testimonies, the committee will decide whether to issue indictments and forward the case to the courts.