I left Dec 27 to Vietnam came back Jan 3, on staying 97 days on my first dtv stay. Pretty cheap to fly just 1:40m away and the country itself is cheap but USA requires a $35 usd visa. If you’re purely bottom cost KL you might be able to do a same day flight run but you’ll need to book separate flights
After hearing your paperwork story I think bouncing in n out of the country might be easier.
why? the extension is IF you want to stay longer than 6 months, without leaving the country. Anything else, you'd be doing more work, and possibly spending more.
I once applied twice for a tourist visa to Thailand and had my passport number autofill - and twice had it denied over wrong passport info. I had one extra digit duplicated I missed twice. Both times visa fee used up.