Recently, though, portraits of the king's son, Crown Prince Vajiralongkorn, have increased as the kingdom of Thailand prepares the groundwork for its first royal succession in nearly 70 years.
In the capital, Bangkok, city authorities have erected gold-framed portraits showing the Crown Prince as a child with King Bhumibol, the pair wearing matching suit and ties. Others show him as an adult standing next to his father.
"There are more portraits of the Crown Prince now than a few years ago," said a palace source. "This is not by chance, but it is a way to try to pre-empt any future instability." The source declined to be named citing the sensitivity of referring to the succession and the death of a venerated king.
The evening news on state television channels, which has a daily segment on Thailand's royal family, also has increasingly featured the prince and his family, including coverage of their trips abroad and attendance at seminars, sporting events and fashion shows.
The thrice-married prince and his family -- two daughters from his first and second marriages, and a son from his third -- are seen more frequently on state television and in glossy magazines.
King Bhumibol, who assumed the throne in June 1946, is in failing health and has been confined to a Bangkok hospital since last May. He was recently treated for hydrocephalus, or 'water on the brain', according to the Bureau of the Royal Household, and is recovering from a fever and infection.
Most Thais have known no other king. Bhumibol's succession has prompted worries about instability in a country that has witnessed 19 coups or attempted ones and at least 19 constitutions since a constitutional monarchy replaced an absolute one in 1932.
The current military government, which took power after a May 2014 coup following a decade of political conflict, has unveiled yet another draft constitution that allows it to keep extensive political powers during a transition period to follow a general election scheduled for mid-2017.
ROYAL PR MACHINE
An opaque and secretive public relations machine is helping to prepare for the succession. It includes the Bureau of the Royal Household, which handles some of the monarchy's public relations, the Office of His Majesty's Principal Private Secretary, and both public and private institutions.
The Office of His Majesty's Principal Private Secretary, which coordinates between the monarch and the government, must approve all public displays of the royal family, including the portraits of the prince adorning buildings and lamp posts in the capital. The office, which is part of the royal household, turned down a request from Reuters to interview its staff and observe its work.
"Even though what we do is no secret, we have no policy that allows this," the office told Reuters in a statement.
King Bhumibol has endeared himself to Thailand's 68 million people through his well-publicised efforts in rural development and conservation.
He is often referred to as 'father' and his birthday, December 5, is celebrated as father's day. Daily news coverage of the royal family and standing up at the cinema for the king's anthem are all part of Thai life.
The military government has significantly increased the budget for "upholding, protecting and preserving the monarchy" to 18 billion baht ($513.70 million) in the 2016 fiscal year that began in April, a 28 percent increase from two years ago when it took over. Some of the money is earmarked for community and rural development projects.
The junta has also been cracking down on critics of the monarchy using Thailand's strict lese-majeste law -- a French term for the crime of offending the dignity of a sovereign. Last year, there was international condemnation when two people received jail sentences of 25 years and 30 years on lese -majeste charges for Facebook posts about the king.
'BIKE FOR DAD'
Crown Prince Vajiralongkorn, 63, has taken over most of his father's ceremonial duties but has yet to command the same veneration, experts on the Thai monarchy say.
He is portrayed as a devoted father and family man. The prince and his daughters led thousands of cyclists through the streets of the Thai capital Bangkok in December to mark King Bhumibol's 88th birthday.
Video footage of the prince and his young son cycling together were played frequently in the days leading up to the 'Bike for Dad' event.
In one clip from the cycling event used frequently by public news channels, the lycra-clad prince cycles across a public square in Bangkok and waves to the crowd, who shout: "Long live the king!"