The quite distinctive Blue-tailed Bee-eater (Merops philippinus) is green overall with an orange-chestnut lower throat, black eyestripe and bluish rump/tail with long tail-streamers. 
The juvenile has a duller lower throat and lacks tail-streamers.
The bird is migratory and has a patchy breeding distribution across India, Myanmar, and parts of Southeast Asia but it can be seen in the south of Vietnam during the entire year.

Ben Tre area, Mekong Delta, Vietnam, 24 December 2023