Here are some of the definition for addressing the Thai monks in Thailand.
•หลวงพี่ or “LUANG PHI” is classified for a young monk.
•หลวงพ่อ or “LUANG PHO / LUANG PHOR” is classified for a middle aged monk.
•หลวงปู่ or “LUANG PU / LUANG POO” is classified for a old renowned monk.
•หลวงตา or “LUANG TA” ( classified for becoming a monk at older age ) is less respectful that “LUANG PHO / LUANG PHOR”.
•หลวงเถระ or “LUANG THERA” is classified for a man being a monk for 10 years.
There are numerous famous Thai monks that are worth mentioning for their contributions of building Thai temples and helping those people who were in need at that point of time. You may have heard about their stories and contributions as it spreads around the world for what they did during their lifetime. Some of these monks that we are talking about will be L.P. Suk Gesaroh, L.P. Yiam, L.P. Pae, L.P. Pahn, L.P. Tae, L.P. Toh Itatsuwannoh, Somdej Pra Sangkarat Pae Wat Suttat, Tahn Jow Koon Noh, L.P. Koon, L.P. Waen, L.P. Kasem Kemagoh, L.P. Prom Wat Chong Kae, Phra Krubah Seewichai and they had done very much for the Thai people during their lifetime.
One of them which I like to mention about will be L.P. Kasem as he had passed away in BE2538 when he was 83 years of age. He was the descendant of Lampang’s King during the period of Lanna. He was a monk in BE2468 and became the abbot of Wat Bunyeum after his uncle passed away. During his monkhood, he was good at sammahdti and had been to forests and cementries for Tudong. He was a person with great learning and knowing of life was filled with uncertainty, he went to Sasahn Sahlahwangthan cementry where he practise the highest sammahdti. At that time, he had sat on the burial ground while watching the burning of the corpse. Regardless the weather was hot or raining, he would simply be quietly sitting on the burial ground as he watched the corpse being slowly burned into ashes.
It was written that L.P. Kasem had done in sammahdti for the entire 3 months under the hot blazing sun and even when it was under thunderstorm without having shelter at that moment. It was said that his robes were wet with rain water and even during cold season with cold wind blowing at him, he would simply sitting quietly without a single complain. It was also mentioned that he had done his practise of dhamma and sammahdti without food for the entire 49 days period. It was surprisingly to learn that L.P. Kasem took his bath once a year without any stench or foul smell on his body as he sweated during the hot summer days. An a much more surprising thing was that even he did not stayed in any shelter while practising, L.P. Kasem never had any bite from the mosquitoes at the cementry.
It was told that his worldly possession was simply just his robe, alm bowl and a piece of human bone used for practising sammahdti and walked bare footed. Any types of offerings that layman gave him was given away to other monks. He would sleep in the full protrate position without any pillow as he considered it as luxury and slept on the same spot while doing sammahdti.
As we know from his biolography, L.P. Kasem was a simple person who was determined to understand the real meaning of life as he had asked nothing in life even though he could have enjoyed a luxury life for being the descendant of royal blood in Lampang.
You can read more about the stories of other famous Thai monks and their contributions.