Should we each bring our own carry-on or share one checked bag?

Each person should have their own carry-on. Sharing a checked bag means if it's delayed, both of you have no clothes. Carry-ons also let you move between cities faster without waiting at baggage claim. Pack shared toiletries and medications split between both bags so you have backups.

How much should we coordinate our outfits?

Coordinate one temple outfit and one nicer dinner outfit so you can do those activities together without one person being under or overdressed. Everything else can be individual. Matching too much looks awkward in photos and limits your options if one outfit gets wet or dirty.

Do we need to pack dress clothes for nice restaurants?

No. Southeast Asia is casual even at higher-end places. A sundress and a collared shirt with chinos is as dressed up as you need. Anything fancier will be uncomfortable in the heat and look out of place. Save the luggage space for beach clothes and temple-appropriate coverage.

Should we bring fancy camera equipment as a couple?

One decent smartphone camera is enough for most couples. Hauling a DSLR means one person is always the photographer while the other waits. Phones let you take turns easily and don't require a separate bag. If one of you is serious about photography, bring a mirrorless camera and one lens — the other person shouldn't have to carry backup equipment.

How do we pack for both beach time and city temples?

Bring 2-3 swimsuits each, 1-2 beach coverups, and 1 temple-appropriate outfit that also works for nicer dinners. Your everyday shorts and t-shirts work for cities when temples don't require coverage. A sarong can double as a beach coverup and temple skirt. Don't pack separate wardrobes — everything should do double duty.

Pack for a Couples Trip to Southeast Asia

For a couples trip to Southeast Asia, each person needs 5-7 lightweight outfits, shared toiletries to save space, and layers for heavy air conditioning. Coordinate one nicer outfit each for temples and dinners, pack a shared first-aid kit, and bring reef-safe sunscreen you can't easily find there. The region is hot and humid year-round, so quick-dry fabrics are non-negotiable.

Divide shared items between bags. Put toiletries in one person's bag, first-aid and medications in the other. If one bag gets delayed, you still have essentials. Share sunscreen, bug spray, and any travel-size laundry detergent. One phone charger block with multiple USB ports beats two separate chargers.
Pack coordinated temple-appropriate clothing. Each person needs one outfit that covers shoulders and knees for temples. A lightweight linen shirt and pants work for both. Many temples rent sarongs, but having your own means you can visit spontaneously. Avoid having to buy overpriced coverups at temple entrances.
Bring one nicer outfit each. A casual dress and a button-down shirt with chinos cover rooftop bars and nicer restaurants. These double as temple clothes if they're modest enough. Everything should be wrinkle-resistant because hotel irons are unreliable.
Pack quick-dry everything. Humidity means laundry takes forever to dry. Merino wool and synthetic blends dry overnight on a hanger. Cotton takes 2-3 days and smells musty. Each person needs 5-7 shirts, 2-3 shorts or skirts, 1-2 pants, 7 underwear, and 1 light jacket for over-air-conditioned buses and restaurants.
Split one shared day pack. Bring one 20-25L daypack for both of you. It carries water bottles, sunscreen, a small umbrella, your nicer outfits if you're changing for dinner, and anything you buy during the day. Taking turns carrying it is easier than each hauling a small bag.
Pack reef-safe sunscreen from home. Reef-safe sunscreen is hard to find in Southeast Asia and costs 3x more when you do. Bring 2-3 bottles of mineral-based SPF 50. You'll go through more than you think between beach days and walking around cities in direct sun.
Coordinate medication and first-aid. One person carries the first-aid kit with bandaids, antibiotic ointment, and blister treatment. The other carries medications. Both of you need anti-diarrheal meds, electrolyte packets, and any prescription medications with extra days built in. Assume you'll each have at least one stomach issue.

Should we each bring our own carry-on or share one checked bag?: Each person should have their own carry-on. Sharing a checked bag means if it's delayed, both of you have no clothes. Carry-ons also let you move between cities faster without waiting at baggage claim. Pack shared toiletries and medications split between both bags so you have backups.
How much should we coordinate our outfits?: Coordinate one temple outfit and one nicer dinner outfit so you can do those activities together without one person being under or overdressed. Everything else can be individual. Matching too much looks awkward in photos and limits your options if one outfit gets wet or dirty.
Do we need to pack dress clothes for nice restaurants?: No. Southeast Asia is casual even at higher-end places. A sundress and a collared shirt with chinos is as dressed up as you need. Anything fancier will be uncomfortable in the heat and look out of place. Save the luggage space for beach clothes and temple-appropriate coverage.
Should we bring fancy camera equipment as a couple?: One decent smartphone camera is enough for most couples. Hauling a DSLR means one person is always the photographer while the other waits. Phones let you take turns easily and don't require a separate bag. If one of you is serious about photography, bring a mirrorless camera and one lens — the other person shouldn't have to carry backup equipment.
How do we pack for both beach time and city temples?: Bring 2-3 swimsuits each, 1-2 beach coverups, and 1 temple-appropriate outfit that also works for nicer dinners. Your everyday shorts and t-shirts work for cities when temples don't require coverage. A sarong can double as a beach coverup and temple skirt. Don't pack separate wardrobes — everything should do double duty.