How much corporate tax would I really have to pay in Thailand?

I've read that it's 15% or 20% depending on your net profit. The official numbers are easy to find. But I've also read that you need to hire four Thai employees, and I know now that there are methods to circumvent this requirement.

Therefore I'm wondering if there are some "tricks" to avoid paying that much tax too?

Sorry if my question comes across as cynical, but I need to know this before I decide to form a company in Singapore instead of in Thailand. As we all know, the official law here often doesn't reflect reality. I just want to know what to expect.