@Kris ********
Because you must transfer 800k baht to sit in a Thai bank (exchange costs). Interest is almost nothing (or nothing) and if/when you eventually want to transfer it back, there's the hassle (Thailand has stricter transfer out rules), and exchange cost plus rate may/may not be worse.
Keeping that $ in a CD pretty much pays for agent to handle it all for you with no exchange hassles/risks.