Should we each carry our own large backpack?

No. Navigating busy markets and public transit is significantly easier when one person is responsible for the main bag while the other manages smaller daypacks. Switch who carries the main bag every travel day.

Do I need a raincoat?

Yes, but don't pack a heavy one. Buy two lightweight, packable rain ponchos. You will encounter sudden tropical downpours regardless of the season.

How to Pack as a Couple for Southeast Asia

Pack one shared 60L-70L duffel or backpack and two small personal item daypacks to keep your load under 15kg total. Focus on lightweight, breathable fabrics that dry overnight and prioritize shared essentials to save space.

Use a modular packing system. Buy two distinct sets of packing cubes, one color for each person. This keeps your clothes separated within the shared bag so you aren't digging through each other's items.
Limit to one week of clothes. Regardless of how long you travel, pack for 7 days. You will have access to laundry services everywhere for roughly $1-2 per kilogram. Aim for 7 shirts, 3 shorts/skirts, and 1 set of 'temple-appropriate' long pants.
Consolidate toiletries and tech. You only need one bottle of sunscreen, one tube of toothpaste, and one universal travel adapter. Share these items instead of packing two of everything.
Prioritize footwear. Limit yourselves to two pairs of shoes each: one pair of durable walking sandals and one pair of lightweight sneakers. Wear the heaviest pair on the plane.

Should we each carry our own large backpack?: No. Navigating busy markets and public transit is significantly easier when one person is responsible for the main bag while the other manages smaller daypacks. Switch who carries the main bag every travel day.
Do I need a raincoat?: Yes, but don't pack a heavy one. Buy two lightweight, packable rain ponchos. You will encounter sudden tropical downpours regardless of the season.