[sarasi]

In Japan that would most likely fall under the Cultural Activities visa. To get the cultural visa you would have to have proof that you are already seriously studying that aspect of Japanese culture, i.e. already have an established meditation practice and be pursuing studies in Buddhism before applying for the visa.

I imagine that Thailand and Laos have a similar system, or it may be that the foreign monks do "visa runs" over the border every few months, which apparently Thailand is less strict about than Japan is.