Many forest bhikkhus in North-East of Thailand use the word 'Buddho' as their meditation object. They use it as a kind of koan, firstly they calm the mind by following the inhalations and exhalations using the syllables 'Bud-dho' and then begin to contemplate 'What is Buddho, the "one who knows"?' 'What is the knowing?' When I used to travel around the North-East of Thailand on 'tudong' I liked to go and stay at the monastery of Ajahn Fun. The main part of his teaching was to not just mechanically repeat 'Buddho' but to reflect and investigate, to awaken the mind to really look into the 'Buddho', the 'one who knows', really investigate its beginning, its end, above and below, so that one's whole attention was stuck onto it. When one did that, 'Buddho' became something that echoed through the mind. One would investigate it, look at it, examine it before it was said, after it was said and eventually one would start listening to it and hear beyond the sound until one heard the silence.