Royal Billboards in Thailand

Big billboard of the Crown Prince in Ubon

All over Thailand you can see big billboards dominating intersections, showing pictures of the King. Sometimes the Queen, occasionally the Princess, but the Crown Prince (Maha Vajiralongkorn) gets rather less play. Except in Ubon Ratchathani, where he seemed to dominate - it is his picture above, taken in Ubon. Wikipedia in their entry about him quotes the Economist (I didn't check the original source) as saying in 2002 that "Vajiralongkorn is held in much less esteem [than the king]. Bangkok gossips like to swap tales of his lurid personal life. One of his sisters, another possible heir to the throne, is more popular, but Thailand has never been ruled by a woman. Besides, no successor, however worthy, can hope to equal the stature King Bhumibol has attained after 55 years on the throne." I wondered if perhaps there was some strong association between Vajiralongkorn and Ubon, but a short internet search turned up very little.