Do some research on expected wind, I was in Thailand last week & the kite school I visited on Kho Phangan was just closing for the season.. there was not a puff in the 3 1/2 weeks I was there. You may get some early wind from the start of the new season or some squall fronts if you're really keen, but I think you may get nothing in that area in july. Probly not worth carrying kites on the off chance.
The place I went was just over AUD $100 per day for gear hire - relatively expensive (compared to living/eating/etc)but that was for your choice of new 06 north/naish gear - worth testing out I'd say.
Considering that you *could* get hit with hundreds in excess baggage fees, not to mention lugging it around, I'd say hire. Excess baggage seems pretty random, I went round the world a few years back with a 26kg kite bag & an 11kg (small) backpack, never even came close to getting charged excess. Have heard plenty of horror stories tho.
Vietnam in July has steady strong cross onshore winds, the place to go is called Mui Ne which is about 3 hours bus ride from Ho Chi Minh City (Saigon). Theres an aussie guy called Campbell who runs a shop and rents gear off the beach, from the Sailing Club Resort. As far as taking gear I would probably take it, or contact airwaves.com.vn to see how much to rent. good luck.
