Hi Brian, Not a "Priest knife" IMHO but a Dha dagger as stated above. Look here
http://dharesearch.bowditch.us/ and go to the task bar at the bottom. I think you will find there all you need to know.
As for the Monks carrying knives....I understand that these were more a religious talisman/amulet and as such can be bought today in the Thai markets. What you have there is NOT a Priest knife.
Is the hilt ivory?
Stu