Scene at BTS Saphan taksin

Two Americans were looking around and confused if the train that is currently on the platform is the one they should take. They seem very nice so I did not hesitate to approach them and help.
To cut the long story short, one of them commented " your english is good"
For a quick second I was juggling with two responses:
A) I'm not Thai
B) I'm Filipino

I opted to respond with B). And I hope you know why.