Thailand's lese-majeste suspect Suriyan Sujaritpalawong (C) is escorted by police officer as he arrives at military court in Bangkok, Thailand, October 21, 2015. Reuters

Reuters/Bangkok

A man arrested as part of a high-profile royal insult investigation in Thailand has died, the justice ministry said on Monday, the second suspect in as many weeks to die in police custody.
Suriyan Sucharitpolwong, a well-known fortune teller and former aide to Crown Prince Maha Vajiralongkorn, was admitted to hospital on Thursday and died of natural causes on Saturday, the Department of Corrections said in a statement.
Suriyan died of a "blood infection", the department said.
Suriyan was charged with lese-majeste, which in Thailand is one of the strictest such laws in the world, along with two other people involved in an alleged conspiracy to exploit the name of Crown Prince Vajiralongkorn.
Thailand's royal insult laws carry up to 15 years in prison for each count for anyone convicted of insulting the king, queen, heir or regent.
Until his arrest, Suriyan had been seen frequently with top officials. He was also the chief organiser of a cycling event in August which the prince took part in, in honour of his mother, Queen Sirikit.
Another suspect, Prakrom Warunprapa, a prominent policeman, died in custody last month. Police say he hanged himself using his shirt but refused to do an autopsy.
The investigation is part of a crackdown on perceived royal insults launched by the junta, which took power in a coup last year.
Ultra royalist Prime Minister Prayuth Chan-ocha has vowed to stamp out critics of the monarchy but some say the crackdown is aimed at ensuring an orderly succession.
King Bhumibol, 87, is convalescing at a Bangkok hospital after being treated by doctor's for 'water on the brain'.
His frail health has added to the political uncertainty surrounding Thailand since the 2014 coup.
"This is a very sensitive time for Thailand and part of the reason that the military is in power is to ensure a smooth royal succession when the time comes," said a Bangkok-based political analyst who declined to be named because of the sensitive nature of the issue.
Nervousness over the succession has formed the backdrop to a decade of political crisis in the country. The lese-majeste law prevents any open discussion of the succession.
National police chief Jakthip Chaijinda said police were waiting to issue more arrest warrants, including for military officers, in connection with the investigation.