Start from the bottom:
There's only one 2-letter word LA, so it goes at the very bottom middle. Then there's only one 5-letter word with L in the middle, so STLKF goes there. We can rapidly fill in around that to get to here:
Now consider the 3-letter words beginning with P.
If it's PIA, then the 4-letter word ending with I must be PREI, but there are no 5-letter words ending with P. So it's PCB and then AADC, and then we can rapidly fill in NTB, DTE, DIE, AANG, AGE, and there are only two 5-letter words ending with A which share the same penultimate letter, so they must be DRAMA and OBAMA in some order.
Also from AGE there must be a 6-letter word beginning with A, whose fifth letter begins a 7-letter word, so that must be INDOSAT. Also the fourth letter of that 6-letter word must be A; it's also the fourth letter of a 5-letter word which must be ORMAS or ZAKAT, and the second letter of that is the fourth letter of a 6-letter word, so we can fill in ZAKAT, ZEN, TNI, NANTI, then ALBAIT and ASSAIA, then YENISEI going up and SOY.
Now in the top right we have limited possibilities:
The only 2-letter words with O in the middle are AON and SOY, but its first letter must be the last letter of a 7-letter word, so it's AON and WICHITA, then NEA, RTS, CHIEF, SWIPOA, FBI.
Two to the left of SWIPOA is another 6-letter word; its first letter is the second letter of either CPNSS or RAKSA, and its third letter is the second letter of either ANGIN or DUNIA. So we can fill in PIUDDR, CPNSS, DUNIA, SIA, CND, DUO, RUROUNI, and also ANGIN, MBA, LEM back on the right.
Now there's only two 6-letter words and two 7-letter words left (AOPMES, RIYALS and ABSENSI, OAKLAND), all over on the left-hand side and connected to each other. The only way we can do that is as follows:
Now there's lots of other stuff to be filled in around those long words on the left, and some other deductions which lead us all the way to the centre.
Now only four 5-letter words remain to be used:
ALIEN, KOBRA, MINTA, RAKSA. All of them can be filled in directly from the single letters we have for each of them.
And all that's left is 3-letter words, which we painfully fill in using whatever deductions we can use.
Firstly NIP, KIM, PIA, OEK in the lower left (only one word left beginning with N, and the rest falls into place).
Then BEL, BRI, TEA, TUA in the upper left (only one word left ending with L) followed by IUR, AIR, RIO, HBO in the extreme top left (only one word left with U in the middle).
Then RAI, ALI in the lower left (only one word left beginning with R). The word beginning with BA could still be either BAK or BAR, but there's no other word ending with AR, so it must be BAK and IAK.
Finally QNF, QNT, BNI, BAR in the extreme bottom right.
For the thematic hidden messages, I defer to Gareth's superior knowledge of
Indonesian Indonesian puzzles :-)