This is a Pacific Swallow (Hirundo tahitica). Size 14 cm (5.5 inches).
Deep metal blue upperparts and smoky grey underparts. Chestnut throat
and forehead. It has a slightly forked tail. Undertail coverts has scale
like marking. It is a common resident from low elevation to 1800 m
ranging South to Singapore and is found in open country, forests and in
towns and cities. It often nest in sheltered walkways and other man made
structures such as under bridges and flyovers.