Noppadon Pattama, who is also Thaksin's legal adviser, confirmed yesterday that Thaksin will make the private visit to Myanmar, which wraps up on Saturday.
On Friday, Thaksin will meet leading government MPs from Thailand and Thai and Myanmar businessmen in Tachilek, a border town opposite Chiang Rai.
There will be no business deals made during the meeting, Mr Noppadon said.
The former prime minister will make merit at a replica of the Shwedagon Pagoda in Tachilek on Saturday.
"This is the closest that Thaksin has come on a trip to a country, but Thaksin has no hidden agenda. The former prime minister will just meet with President Thein Sein in his capacity as an old friend," Mr Noppadon said.
Mr Noppadon suggested that red-shirt supporters who wish to greet Thaksin in Myanmar stay overnight on the Thai side of the border on Friday before crossing over the next morning, as more hotel rooms were available in Thailand and at cheaper rates than in Tachilek.
He dismissed rumours that Thaksin's trip to Myanmar involved investment in the Dawei deep-sea port.
"Investment in the Dawei project is a matter between the Thai and Myanmar governments," he said.
He did not believe Thaksin would use the opportunity to console Pheu Thai MPs who missed out on ministerial posts during the recent cabinet shake-up, saying no one would raise the issue with the exiled leader.
The Myanmar government has already given the green light for the red shirts' trip to Tachilek to meet Thaksin, Mr Noppadon said.
He shrugged off a question about whether the Pheu Thai government might feel uneasy about Thaksin coming so close to Thailand, saying it was not the duty of the government but of Interpol to arrest the former prime minister. The warrant for Thaksin's arrest was a product of the coup that overthrew his government, and so the warrant itself violated the rule of law, Mr Noppadon said.