Originally Posted by transpac

Or was there some fee, in his "native" currency, which somehow converted to exactly 150 THB?

Based on the facts that you've provided my best guess is that your colleague's home bank has probably applied a fee, perhaps he was allowed some number of complementary withdrawals, after which a fee is applied, or the fee will be subsequently credited, or it was incorrectly applied.

I think the main takeaways from your story are that your colleague's issues are with his bank rather than AEON, and that AEON still provides fee (Thai banker's 150 baht fee)-free ATM withdrawals