I received a reply about this very question from Ajahn Achalo, himself. Very thankful for the time he took to write this response.
It’s curious… for although there are high level Bodhisattva practitioners in Thailand, they are rarely referred to as such. It is actually my Arahant teacher who tells me which ones are Bodhisattva practitioners when I ask him. Tahn Ajahn Anan can simply see these things with the abilities of his purified mind. That monk who you mention - Luang Por Klien is about 100 years old now and in quite poor health, not really teaching or receiving guests unfortunately. Perhaps this discretion is out of deference to the general paradigm of Theravada as many people understand it… to aspire to Arahantship as swiftly as possible?
As far as I can tell, there are not actually Bodhisattva or Mahayana lineages practicing here in the Theravada form
anyway (Although there are some Vietnamese Mahayana monasteries I believe) Rather there are a few great monks
who practice within our form. Many of the truly great ones have passed away recently sadly, and it is rare that their
students are as gifted as them. Luang Por Uttama, Luang Por Soopha come to mind as great monks who were clearly Bodhisattvas. Both actually walked to India and back as younger monks! They passed away in their ninetees I believe. The ‘Bodhisattva monks’ often clearly have psychic powers and use them to help people overcome their challenges by giving advice in all realms of life - in a more obvious and public way. Arahants with psychic powers will tend to share these abilities only with closer students, and have more of a focus upon teaching the basics of Buddhism. A wisdom approach.