Do I need a special visa for multiple entries into Thailand within 90 days?

Hello,

I'll be heading to Thailand in September.

I want to know if I need a special Visa for my itinerary.

Thailand (Sept 6th - Oct 3rd)

Indonesia (Oct 3rd to Oct 17th)

Thailand (Oct 17th to Nov 5th)

Cambodia (Nov 5th to Nov 12th)

Thailand (Nov 12th to Nov 30th)

That's 3 trips into Thailand within 90 days, but I'll only be in Thailand for around 60 days.

Do I need a multi-entry? If so, how do I go about getting one? I'm from the US btw.