You should have no problem with the security checks or transfer at Narita. There is an Elite line for you to go through at security. And as the NRT-BKK flight is usually a 747 or 332 you should not have to worry about the bus. The buses are usually for the 757s.

Have a great trip and enjoy the WC at NRT. The one on the second floor offers a great view of all the NW metal as well as the runway where the heavies are taking off and landing.

NGO-NWA