The blue pearl, a wooden bar on the water that you reach by a wooden pier.
It's the best place for sunset. As it belongs to Koh Mak Coco cape Resort, you might need to pay a fee to get in.
Cinnamon Scenic Boardwalk, a very long wooden pier, very cool from drone.
Ao Soun Yai Beach (see above), where you can have lunch or a drink in Seavana Beach Resort Koh Mak. Sunsets are very nice here too
Koh Kradad, another private island home to a herd of deers.
For food, I recommend the Mak Trat, very nice restaurant with a very nice pool, good cocktails, and a nice view. You can also try Food art hut, for very nice breakfast and coffee.
Only one thing to be careful here: sand flies, make sure to get a repellent before heading there.