One of your biggest problems is going to be Avgas if you are flying avgas. I am based in Kolkata and I dont think they have avgas here, unless of course your in a Jet fuel powered GA plane... why dont you let us know what you are planning to fly in and we might be able to help some more....
For myanmar here is a man who will get your overlflight clearance for $25 Nay Tun Thoung Wonderful Golden Land Travels & Tours
[email protected] .
Thailand we use Anadaman Andaman Aviation Services
SITA: BKKAAUV AFTN: VTBDUVAA
Mob.: +66-81-8341943 (Pawel), +66-81-8350080 (On Duty)
email:
[email protected],
[email protected],
[email protected]
Although you technically can apply for both these permits on your own via the respective websites.
China we have a office in Kunming we fly to (although I personally havent done the trip yet) but we use Universal for the clearances, which are really really expensive, on the ground we use Air China to get our clearances and fuel. But if anyone knows a handler who can get the Chinese clearances post it here or pm me, would rather go direct to a person in China and cut out the expensive middle man. Also remember China Crew Visa will probably be needed, and it takes time to get!
Are you based in Kolkata (there are only 4 GA planes here that I know of), or you flying in from some where else? If you need a hand on the ground in Kolkata if you arent based here PM me.