BANGKOK — Thailand's army has detained an activist who wrote on Facebook that he would wear the politically charged color of red to mark King Bhumibol Adulyadej's cremation this week.

A lawyer for Ekachai Hongkangwan says soldiers arrested Ekachai at his Bangkok home on Tuesday morning and indicated they would detain him outside the city.

Ekachai commented on Facebook last week that he would wear red on Oct. 26, the day Bhumibol will be cremated during an elaborate five-day funeral, and "do what people least expect."

Ekachai previously served nearly three years in prison for violating Thailand's draconian lese majeste law by distributing copies of an Australian documentary on the Thai royal family.

Supporters of elected governments ousted by Thailand's military in 2006 and 2014 are known as "Red Shirts."