Hi Sadalsuud,
I have no direct experience but four things came to my mind. Maybe they are a good start for further research.
First one is the american monk
Ajahn Sumano Bhikkhu who lives in the Double-Eyed Cave Retreat, at Pak Chong in Thailand's Khao Yai National Park. I saw some interviews and it looks pretty solitary. But I'm not sure if he welcomes long-time guests.
Second is the
Antaiji monastery in Japan. The abbot is a very nice guy from Germany. But it would probably be too far away for you?
Third one is a
documentary on hermits in the chinese Zhongnan Mountain Forest Park that I watched a few months ago. Looks very nice but the trip would probably take too long. And it's probably very tough to contact anyone up there.
Fourth is Ajan Brahm. He very often travels to Singapor and the contiguos countries, as far as I know. And he has spend some time in hermitage around that area. Maybe you contact him or his students via the
Bodhinyana Monastery website or the
Dhammaloka forum community.
Have a great trip!