Yeah that, also this is south east Asia, not middle east. War (especially between countries) are so rare here.
Indo-China has had a ton of war in 20th century though....really bad blood simmers between a lot of them deep down and also the VN-PRC one that PRC escalated in 79 along with the SCS 9 dash line spratly stuff they assert for no good reason that makes things worse.
Indonesia is just far enough away and is on islands with few borders compared to say Burma-Thailand-Cambodia-Vietnam-Laos area....with China above and India to west etc.
Thailand Cambodia one, well there was lot of bad blood during Vietnam war (Thailand was major US ally and staging area) and then with Khmer rouge and Vietnamese intervention there that made Cambodia a simmering proxy war between Vietnam/USSR vs Thailand/US/PRC for quite a long time even after pol pot fled to border jungle area.
So these two Hindu temple (candi in Indonesian term) are again friction point like the last one in 2011 or sometime ago....as they are significant to cultural basis/assertion and are both very close to border (I think preah vihar was referred to arbitration and awarded to Cambodia fully in the end).
The issue becomes one of flexing the older bad blood on. Still it is very unlikely to escalate to something bigger as Thailand is far more dominant developed economy to Cambodia, like was the case already during last flare up in same areas.