My guess is, that The King is simply not interested in the duties but only in the benefits that his status as a Thai Royal brings - he led the life of a playboy for decades and never really carved a sensible role as heir to the throne (in comparison to other heirs). He seems a rather selfish character. A pity, he didn't renounce his rights to the throne in benefit of his younger sister HRH Princess Maha Chakri Sirindhorn. She is "the daughter of her father" (character wise), caring, interested in the country's people welfare, dutyful and she's loved and honoured by the Thai people. The Princess would have been a splendid Queen!