For safety items the certification or strength decides whether the product protects you: a mask without N95/KN95/P2, a repellent without enough DEET or icaridin, or a filter coarser than 0.1 micron does not do the job.
Preparedness
Key specs used in the panel, in plain English:
Masks: only certified respirators filter PM2.5: N95 (US NIOSH), KN95 (China GB 2626) or P2 (Australia/NZ), printed on the mask. Cloth and surgical masks do not.
Water filter: a hollow-fibre membrane rated 0.1 micron removes bacteria and protozoa but not viruses or chemicals: still boil or chlorinate doubtful water.
Bleach for water: the label must say sodium hypochlorite 5-6%, unscented; colour-safe bleach is not chlorine.
Repellent: DEET 20-30% or icaridin (picaridin) about 20% on the label (US EPA-registered actives).
ORS: pharmacy oral rehydration salts (WHO formula), not sports drinks.
Power station: LiFePO4 battery (long life, safer); size it in Wh. A phone charge is about 15-20 Wh, a USB fan 5-10 W; a fridge needs about 1 kWh per day.
Power bank: 20,000 mAh is about 74 Wh; buy a known brand with the Thai TIS mark.
Air purifier: HEPA, with a CADR / room size at least as big as the room you seal.
Water tank / jerrycans: food-grade, opaque, tight lid (no algae, no mosquitoes).
Why it matters for Koh Samui
In an emergency you rely on the item working the first time. Fakes and under-spec products are common online and look the same in photos.