RichieP gave some pretty good advice.
The only thing I would change would be adding in China.
This would be my itinerary for 4 months if I could swing the flight / travel costs. Considering I haven't been to these locations and wanted to knock out most of my Asian bucket list.
Thailand - 3 weeks
Cambodia / Laos / Vietnam - 3 weeks
Philippines - 2 weeks
Japan - 2 weeks
China - 2 weeks
Indonesia - 2 weeks
Taiwan - 2 weeks
The only thing I would change would be adding in China.
This would be my itinerary for 4 months if I could swing the flight / travel costs. Considering I haven't been to these locations and wanted to knock out most of my Asian bucket list.
Thailand - 3 weeks
Cambodia / Laos / Vietnam - 3 weeks
Philippines - 2 weeks
Japan - 2 weeks
China - 2 weeks
Indonesia - 2 weeks
Taiwan - 2 weeks