Below are concise, sourced reviews of well-known sustainable / “responsible” travel companies that run trips in Southeast Asia. For each I give a quick summary, common strengths, typical criticisms from travellers, and links to sources (reviews or the operator’s sustainability pages).

• Intrepid Travel — reliable, industry-leading sustainability commitments; generally strong guest reviews but occasional on‑tour complaints about guides/logistics.

  • Why consider them: carbon-neutral since 2010, B‑Corp, publicly published climate targets and carbon labelling on many itineraries — good transparency for travelers who want measurable footprints. (intrepidtravel.com)
  • Typical traveller feedback: many positive reports about ethical focus and value; some travellers report occasional problems with guides or rushed itineraries (forums/reddits contain mixed personal accounts). (intrepidtravel.com)

• G Adventures — large, widely available small‑group operator with a strong community/Planeterra focus; mixed customer sentiment.

  • Why consider them: formal climate / biodiversity action plan and investment in community projects via Planeterra; broad choice of Southeast Asia itineraries and price points. (gadventures.com)
  • Typical traveller feedback: many very positive Trustpilot and customer reviews praising guides and logistics, but a non‑trivial number of negative/mixed reports on Reddit and review sites about customer service or specific trip problems — expect variability by route and group. (trustpilot.com)

• Responsible Asia (ResponsibleAsia, Hanoi) — Vietnam/Indochina operator that markets itself explicitly as “responsible”; strong local reviews.

  • Why consider them: local operator focused on sustainable itineraries and community/eco experiences (multiple small‑group & private sustainable tours). Traveller reviews on TripAdvisor and TourRadar are predominantly positive (high ratings for guides, eco‑focus and local engagement). (responsibleasia.com)
  • Typical traveller feedback: consistent praise for knowledgeable local guides, thoughtfully designed responsible experiences; good option if you prefer a locally based specialist in Vietnam/Indochina. (tourradar.com)

• Grasshopper Adventures — specialist active tours (cycling/walking) in Vietnam and neighbouring countries; good for active travellers wanting community-level experiences.

  • Why consider them: niche operator focused on cycling/walking with hands‑on local experiences and highly rated customer feedback on their site and review platforms. (grasshopperadventures.com)
  • Typical traveller feedback: many travellers praise guides, pace and local immersion; choose them if you want active/slow travel and small-group dynamics. (grasshopperadventures.com)

• Responsible Travel / ResponsibleVacations (UK-based reseller/ethical tour marketplace) — not a single operator but a curated marketplace of sustainable itineraries in Southeast Asia.

  • Why consider them: they vet and sell tours from smaller local operators and highlight projects they support (education, conservation, community partnerships) — useful if you want vetted, cause-linked itineraries across countries. (responsiblevacation.com)
  • Typical traveller feedback: good when you want an ethical filter and curated options; verify the local operator and recent reviews before booking since Responsible Travel aggregates many suppliers. (responsiblevacation.com)

• Anantara (hotel/resort operator with sustainable programming) — upscale option that runs slow‑travel and conservation experiences in Southeast Asia (hotel‑led, not a tour operator).

  • Why consider them: luxury properties that promote conservation projects, local‑sourcing experiences and “slow travel” packages (good if you’re booking sustainable stays or curated local excursions through a resort). (forbes.com)
  • Typical traveller feedback: positive for quality, but bear in mind hotel‑led experiences are different from small local operators — good for low-impact, high‑comfort stays with conservation add‑ons. (forbes.com)

Practical tips when choosing a “sustainable” operator

• Look for transparency (carbon labels, published targets, local community projects) and third‑party credentials (B‑Corp, verified offsets, SBTi commitments). Intrepid’s carbon‑labelling and public targets are an example of useful transparency. (travelpress.com)
• Check recent, platform‑wide reviews (TripAdvisor, Trustpilot, TourRadar) and read several recent reports — large operators can have excellent averages but local variability; small local operators can be excellent but have fewer reviews. (trustpilot.com)
• Ask operators how they involve and pay local communities, how they handle wildlife/elevations (no riding/handling wild animals), and whether they minimise flights and single‑use plastics. Operators’ sustainability pages or pre‑trip info should answer these.

If you’d like, I can:

• pull recent (past 12 months) traveller reviews for any one of these companies or a specific country in SEA (Vietnam, Thailand, Cambodia, Laos, Myanmar, Indonesia, Philippines, Malaysia, Singapore), or
• find smaller, high‑rated local sustainable operators for a specific country, travel style (cycling, wildlife, cultural homestays) and budget.

(If you want me to fetch up‑to‑the‑minute reviews or current itineraries I’ll pull the latest review pages and listings — say which operator or which country and I’ll get current links and review summaries.)