Most pro fighters don't train this much
In thailand kids/teenagers train this much.
As a part time Muay Thai instructor, I would never recommend anybody ever train more than 4 hours straight anyway, based on everything I know. It isn't wise or helpful.
This is how I trained and was told to train by my teacher who is Samart Payakaroons best friend. He started training at 9 years old with Samart and has fought him twice.
If he tells me to do something, i do it no questions asked.
May I ask you your credentials? How many fights do you have? Because if you tell someone in thailand that you only have the heart to train 4 hours a day they will laugh at you