I Shot the Buddha (A Dr. Siri Paiboun Mystery) - Colin Cotterill

Siri Paiboun and his wife have never been able to turn away a misfit - they share their house with an assortment of oddballs. One of these oddballs - a Buddhist monk - rides out on his bicycle and never comes back, leaving only a cryptic note in the refrigerator: a plea to help a fellow monk escape across the Mekhong River to Thailand. Naturally, Siri can''t turn down the adventure, and soon he and his friends find themselves running afoul of secret service officers and spiritualists.