Diacritics are the whole technical story in Vietnamese search
Vietnamese carries tone and vowel marks that change meaning, and users type queries both with them and without them depending on the keyboard, the device and how fast they are moving. Google handles the two forms reasonably well, but your own systems usually do not. Internal site search, faceted filters, autocomplete, product titles and slug generation all have to decide what to do with marks, and inconsistent decisions create duplicate URLs for the same product, broken canonical tags and category pages that return nothing when a customer types the unmarked form.
There is a second layer that catches even experienced developers. The same word can be encoded in more than one way, as a precomposed character or as a base letter plus a combining mark, and the two versions look identical on screen while being different strings to a database. Content pasted from different sources ends up mixed, and suddenly two apparently identical category names exist. Ask an agency how they normalise text on ingest. If the question surprises them, they have not run a Vietnamese site at scale.
Queries name the city in more ways than the map does
Buyers search for this market under its official name, as Saigon, under the initials of the official name, and under district names, and those queries carry different intent. Searches naming Saigon skew toward informal, local and small business searching. The official name skews toward corporate, government adjacent and international searching. Treating them as one keyword and picking whichever has the larger number in a tool export throws away half the demand and produces a page that matches neither audience well.
District level intent is stronger here than the size of the map suggests. A service business drawing customers from a specific area competes in a different result set than one positioning nationally, and a single page trying to do both will lose to whoever picked a lane. Ask a prospective agency how they would split this, and be wary of an answer that involves creating a page for every district with the same content and a different name in the heading. That approach used to work and now collects nothing.
Google is dominant, but it is not the only search box
Coc Coc, the domestic browser and search product, retains a real user base that skews toward provincial and price sensitive audiences, and it has its own indexing and its own advertising inventory. Whether it matters to you depends entirely on your category, and the way to find out is to look at your own analytics rather than at a market share chart. If your logs show meaningful traffic from it, it deserves separate technical attention, since nothing about ranking there follows automatically from ranking elsewhere.
The larger displacement, though, is marketplace search. A very large share of purchase intent never touches the open web because buyers start inside shopping apps and short video commerce. That reshapes what a website should be for. Transactional queries for physical products are frequently unwinnable on the web, while research, comparison, specification and trust queries are extremely winnable and feed directly into the same purchase. A good partner will tell you which of your target keywords have already been ceded and will redirect the budget rather than spend a year losing.
Conversion ends in a chat window
Zalo and messenger conversations are where enquiries actually happen, and phone numbers still convert better than forms for anything with a considered price. If measurement stops at a web form submission, every channel that works will look broken and budget will drift toward the channels that are merely easiest to count. Event tracking on chat handoffs, call taps and code scans needs to exist before the first month of reporting, not after somebody notices the numbers look wrong.
Social platforms also play an unusual role in credibility here. Many buyers check a company's social presence before trusting its website, so the pages that rank well convert poorly when the social trail behind them is empty. Any proposal that treats search as isolated from that trail is describing half a funnel.
What an SEO agency in Ho Chi Minh City should be able to show you
This is a supplier city as much as a client city, and a significant number of local teams do subcontracted work for agencies abroad. That is not a problem in itself, but it changes the questions. Ask who is on your account by name, how many other accounts those people carry, and whether any part of the work is passed to a third party. Ask to meet the person who will write the Vietnamese content, because content quality varies far more between individuals here than between firms.
Ask also about turnover. Staff mobility in this market is high, and an account that depends on one strong specialist can degrade within a quarter of that person leaving. Documented processes, shared account access and written handover notes are worth more than a charismatic pitch lead.
Technical realities that shape what is worth building
Traffic is overwhelmingly mobile and often on a modest connection, so page weight is a commercial variable rather than a developer preference. Image heavy templates built for showroom appeal regularly cost more in abandoned sessions than they gain in impressions. Hosting choice matters too, because serving from a distant region adds latency that field data will show even when a lab test looks fine.
Local domain extensions require documentation and carry trust with domestic buyers, while an international domain with a language folder serves companies that sell abroad as well as at home. Pick one architecture and commit. The most common inherited mess in this market is a company running a domestic domain, an international domain and a landing page builder in parallel, all competing for the same terms.
Calendar, contracts and the things that quietly stall projects
The lunar new year period effectively pauses commercial activity for longer than foreign planners expect, and the weeks on either side are unreliable for approvals, publishing and supplier response. Any programme scheduled across that window needs the work front loaded. Ask a prospective partner to map their delivery plan against it at proposal stage rather than discovering the gap in February.
On paperwork, agree invoicing currency, tax treatment and intellectual property ownership of content and code in writing. Insist that analytics, search console and domain registrar accounts are created under your own company email with the agency added as a user. These provisions cost nothing while the relationship is good and are the difference between an easy transition and a rebuild when it ends.
Comparing a shortlist properly
Give three firms the same brief, including your real commercial target and your language requirements, then compare their questions rather than their promises. One will diagnose technical debt, one will diagnose content, one will diagnose links, and the reasoning behind each diagnosis tells you how they think. Ask each for an example that went badly and what they changed afterwards.
If the project also needs build work, the local development studios are worth reviewing in parallel, and the wider search agency category is useful context for judging how a local shortlist positions itself. When three names are left, ask for comparable proposals so you are weighing scope and staffing instead of slide design.