The closest FAA from Hong Kong is either Guam or Saipan, I believe that United Airlines operated to both places (pre virus days).
Trend Vector Aviation International Inc, 7-3404 Neptune Avenue Barrigada Guam, GU 96913,
or
Marianas Aviation Services, Corner of Middle Road and Chalan Msgr Guerrero Saipan , MP 96950
I have enclosed a link that might be helpful.
https://www.faa.gov/training_testing...ing_matrix.pdf
Singapore US embassy isn't that helpful these days they will tell you to get in contact with an FAA Flight Standards District Office (FSDO) either in SFO or LAX.
Best of luck.