Check out United Healthcare SafeTrip!! Awesome coverage at the lowest premiums I could find, and I researched the heck out of it. Depending on where you live in the US, you can get a policy for up to 6 months.
I would highly suggest watching the following video from my YouTube channel that will provide you with a massive amount of information, most of which my guess is you haven’t even thought about yet. It’s loaded with great information that I have learned throughout my travels.
BUDGET TRAVEL - Slow Travel - Affordable Travel
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Also, note that Malaysia is Visa Free for U.S. citizens for 90 days. It’s an easy way to do a visa hop when your Thai tourist visa need renewed. But now that it’s 60 days visa free for Thailand, extendable for 30 it’s not so much an issue.
Good luck!!