Where do I find a Buddhist retreat in Asia? I have had experience in meditation, I want to have experience of living and learning with Buddhist monks.  Where in Asia can I experience this for 8 to 10 weeks to start?
Speaking from personal experience with stays at Zen monasteries in Japan: 

It depends on what you mean by retreat. Many Zen monasteries in Japan offer "retreats" in their web pages, but this is not necessarily what is meant in Japanese Zen by a sesshin (接心). If you want to experience the daily life of Buddhist monks in Asia, I'd advise not joining a sesshin for your first time in Japan, as this is an extremely intense period for the monks, and if you do not fully master the local language and the temple customs you will struggle. First time around, I would advise you stay at one or more temples during a regular period.

If you want to sleep, meditate, eat, and work with the monks you can contact the head temple or administrative office of a Buddhist lineage in Japan and ask for possible periods and places to stay (also, indicate if you need some help with the language and customs, as this will be taken into account proposing possible stays to you).

Here are some links you may find useful:

Shoganji Monastery - Rinzai lineage

Soto Zen monasteries for foreigners in Japan - Soto Lineage

ShinShoJi Temple - Rinzai Lineage

Shunkoin Temple - Mindfullness

Japan Vipassana Association

There's also shukubo in Japan, a kind of pilgrim lodging associated with nearby temples.