Privy Council president Prem Tinsulanonda turned up to vote in the charter referendum at a polling unit at Sukhothai School in Bangkok's Dusit district at about 8am on Sunday.
Gen Prem exercised his voting right outside his home constituency, which is in Nakhon Ratchasima province.
The statesman said he was using his right as a Thai citizen and everybody should do the same.
Asked to comment on what the country will be like after the referendum, Gen Prem had no answer, saying he had no part in the country's administration.
He also declined to respond when asked to give his view regarding reconciliation.
