I assume this is a leaf warbler to start with.
"Bright orange color on lower bill without black-tip."
"No obvious wing bar on its wing but a very short white spot on the wings."
If this is the usually leaf warbler with wing bar, this leaves us with only Eastern Crowned Warbler and Goodson's (Blyth's) Leaf Warbler. With thin wing bar, this favours Eastern Crowned Warbler. So as in many cases, description is not sufficient (probably some mistakes) and so no definite conclusion can be made.
HF Cheung
