December East Asia Honeymoon

Hello! My fiancé and I are interested in going to East Asia (likely to Phuket, Thailand) for our honeymoon in December of this year. I am trying to figure out how to plan this out financially in the best way possible (I am going to grad school, so I will be primarily living off of student loans). We are going to be flying out of the midwest, so I understand flights will be *hopefully* no more than $5000. I saw that a Marriott all-inclusive I read about in a different post would be about $900 to stay there for the duration we would have, so it seems a shame to let such a nice vacation be discounted from our list just because of flight costs! Does anyone have any ideas? I have a friend who referred me for the Delta SkyMiles card, but obviously the bulk of the cost would be from flights, so we would not get the bonus miles from spending x amount in the first few months like she did (because she booked a cruise). I would love some recommendations on how to best get the cost of flights down/what credit cards anyone would recommend for this, or even if someone has an idea on an alternate destination that would be similar beach/relaxation vibes (though not the Caribbean, as I have been there a number of times). Thanks!