I plan to do this trip next year..Below is the itinerary that I have made for my future travel.. Before going to Bhutan, you have to obtain travel permit either from Kolkata or when you reach there, latter takes longer time..
tourist going beyond Thimphu and Paro need to acquire a 'special area permit' from the RGoB Immigration Office at Thimphu on any working days (Monday to Friday).
Plan to take a flight to Bagdodara. Take a cab from Bagdodara to Phuentsholing(4hrs).
Take a taxi from taxistand to thimpu( 5 hrs) and halt overnight.
(Norzim lam - main road in thimpu with hotels).
Sightseeing in Thimpu..Tashi Cho Dzong, memorial chortrn,buddha view point,changangkhs hakhang,overnight stay.
Thimpu to Punakha-on way visit Dochula pass, wangriphodrang, punakha dzong,stop of metsina n walk till chimi lakhang., . overnight stay in punakha.(Stay in Dochula Cafeteria lodge for view of snow mountains)
Punakha to Phojikha valley( 3hrs) and Goempa monastery. Overnight stay in Punakha.
Punakha to Paro.(4 hrs). Visit paro dzong, kichu lhakhang,evening walk in paro town,national musuem.
Hike to Tiger monastery or temple. Overnight stay in Paro.
Paro to Ha valley(3 hrs). Overnight stay in Paro.
Return journey to Phuentsholing and then to Bagdodara