Former PM's Office minister and ex-red-shirt leader Jakrapob Penkair will return to Thailand today after 15 years of self-imposed exile.
Writing on Facebook on Tuesday, Mr Jakrapob said: "On March 28 at 7.35am, I will return to serve the country.''
The news was welcomed by his friends and supporters.
Winyat Chatmontri, a lawyer representing former prime minister Thaksin Shinawatra, posted: "I wish you have a safe trip".
Chinnawat Haboonpad, a former red-shirt leader and former Pheu Thai Party MP, wrote: "Welcome. Don't abandon ideology."
Mr Jakrapob served as a government spokesman during the Thaksin government between 2003 and 2005, and he was then appointed as PM's Office minister during the 2008 Samak Sundaravej administration.
Police charged him with violating Section 112 of the Criminal Code, known as the lese majeste law, for a speech he made at the Foreign Correspondents Club of Thailand on Aug 29, 2007. He left Thailand and went into self-imposed exile in 2009.
Public prosecutors dropped the lese majeste charge in September 2011, but following the 2014 coup, the National Council for Peace and Order (NCPO) summoned Mr Jakrapob to report to the NCPO. However, he was still overseas and failed to show up.