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Our serviceBuilt in-houseNo middlemen

Custom WordPress plugin development built to your brief

Custom Plugin Development

The function no off-the-shelf plugin can do, written as a plugin of your own. Works with any theme and any page builder. We start by scoping the requirement, then quote the real job.

Starting price
999 THB/ small function, clear scope
Larger jobs quoted from the spec after we talk
Describe your brief on LINESee example work ↓
Custom WordPress plugin development service by the Southern Whale development team
999 THB
Starting price
Any theme
And any page builder
30 days
Bug cover after handover
100%
Code handed to the client

When ten off-the-shelf plugins still don't answer the one thing you need

What this service is

The problem we see most often: a site owner keeps installing more plugins to get the one function they want. The site ends up heavy, the plugins conflict with each other, and when something breaks nobody can tell which one caused it.

This service means writing a plugin specifically for your site — only what you actually use, with no surplus features to carry. And because the functionality lives in your own plugin rather than inside the theme, you can change theme or update WordPress without losing it.

We always talk first about what the real requirement is, who will use it, and how we'll judge that it's done. Two jobs both described as "write a plugin" can differ tenfold in actual work. Once we've talked, we give you the spec and the price before anything starts.

Why have us write it

What sets this service apart

Written by our own dev team

Southern Whale does this work in-house. Nothing is passed to freelancers or middlemen — you talk to the person writing the code from day one through to handover.

We scope the brief first, always

We don't start coding until we agree on what the plugin must do, who will use it, and how we'll know it's finished. That's why nothing gets delivered that turns out to be unusable.

Works with any theme and any page builder

We build on standard WordPress hooks and filters, so the plugin runs with Gutenberg, Elementor, Bricks, Kadence, Divi, Astra — or a theme you wrote yourself.

You can still update the theme and WordPress

The functionality lives in your own plugin, not buried in the theme's functions.php. Change themes or update WordPress and it doesn't disappear with the theme.

You get all the code

You receive the plugin files with full usage rights. No licence lock-in, no compulsory monthly fee. If you ever want another team to take it over, you can.

Written so someone else can read it

Functions are namespaced with a project prefix, files are split by responsibility, comments are written in plain language, and a short manual comes with the handover.

Examples of what we build

What's possible

If your brief isn't on this list, it's still worth a conversation — almost anything WordPress can do can be written as a plugin.

Forms and data capture
Forms off-the-shelf plugins can't handle — multi-step flows, live price calculation while typing, file uploads that notify your team by LINE or email, with every submission stored in the admin.
Calculators and decision helpers
Work out instalments, shipping, service fees by area, or a ballpark quote. Present the result as a table or chart and attach it to the enquiry form.
Custom post types and tailored admin screens
Your own content types — projects, rooms, courses, client cases — with the fields, filters and management screens your staff will actually use.
External API integrations
Push or pull data with other systems: inventory, accounting, logistics, CRM, chat or Google Sheets. Runs in the background on the schedule you set.
Shortcodes and page builder blocks
Turn your function into a drag-and-drop block in Gutenberg or an element in Elementor and Bricks, so your team can keep using it without us.
Automation and bulk imports
Import large data sets from Excel or CSV, update prices automatically, clean up duplicates, or email scheduled reports.
Fixing the plugins you already run
A small companion plugin that changes how your existing plugin or theme behaves — without editing their source files, so they can still update normally.
WooCommerce tailored to your business
Conditional pricing, discounts for specific customer groups, shipping by region, extra checkout fields, or an ordering flow that differs from a standard shop.
Internal dashboards and reports
A summary screen managers can open in the admin, pulling numbers from orders, forms or outside systems and showing them as cards and charts.

Before you hire us to write a plugin

Limitations, stated plainly

We'd rather you decided on real information than on advertising. If your job shouldn't be built custom, we'll tell you.

1. The 999 THB starting price is for a small function

That price covers work with a clear scope that fits in a single file — changing one behaviour, adding a shortcode, or wiring a form into a notification system. Anything with admin screens, a database, or several API integrations is quoted on the real work after we talk.

2. The brief has to be decidable

If you're not sure yet what you want, we'll spend the first stretch helping you put the requirement into words. That step is necessary, but it does mean coding starts later than many people expect.

3. Some briefs shouldn't be built from scratch

If an existing plugin already does the job well at a sensible price, we'll say so and point you to it. Custom code always carries a long-term maintenance cost.

4. Custom plugins need someone looking after them

WordPress, PHP and the plugins around yours all update every year, so custom code should be reviewed periodically. We can keep maintaining it, or hand it over to your own team.

Suitable for

  • Businesses with a workflow specific enough that off-the-shelf plugins can't cover it
  • Sites that need to talk to other systems — inventory, accounting, logistics or CRM
  • Anyone buying several plugins just to get one function they actually need
  • Sites with so much code in functions.php that changing theme is no longer possible
  • Teams who want staff entering data in the admin instead of editing the front end
  • Agencies who need a plugin development team behind their own clients

Not suitable for

  • Jobs an existing plugin already does well, for less money
  • Briefs where you don't yet know what you want and aren't ready to discuss details
  • Plugins that infringe copyright, unlock licences, or anything nulled
  • Systems that should be a separate app or piece of software rather than forced onto WordPress

From 999 THB, quoted on the real work

Pricing
Small function, clear scope
999 THB
Starting price · one-off payment, no compulsory monthly fee
  • We scope the brief and write the spec first — no charge at that stage
  • Built as a separate plugin; we never edit theme files or WordPress core
  • Tested against the theme and page builder you actually run
  • Plugin files handed over with a short manual
  • Bugs within scope covered for 30 days after handover
Tell us your brief

PromptPay / bank transfer · Invoice available

How we work

Process
1

Talk through the brief

Tell us how the work happens today, where it breaks down, and what you want the plugin to do. We ask questions back until the scope is clear. This stage is free.

2

Spec and price

We write a short spec: what you get, what's excluded, how long it takes, and what it costs. You confirm before any work starts.

3

Build and trial

We develop on a staging site or a copy of yours, hand it to you to try along the way, and revise against what we agreed until it passes.

4

Install and hand over

We install on the live site, test again, send you the plugin files with a short manual, and cover bugs within scope for another 30 days.

Bringing these along gets you a faster quote: the site URL, the theme and page builder you use, screenshots or files that are relevant, and a short description of how things work now and how you want them to change.

Services that often follow this one

Work we do in-house

Hand-coded site to WordPress 100%

Already have a site written in code, but every text change needs a developer? We move the whole site onto WordPress. From 2,500 THB.

Headless WordPress with a static front end

WordPress for editing, static files for visitors — fast to load and hard to attack. From 5,000 THB.

WordPress development and care

Custom WordPress builds, monthly maintenance, fixes, malware removal and migrations — by the same team that writes your plugin.

Web development on a modern stack

Custom sites built for speed and scale, with no templates — for when the brief has outgrown what a plugin alone should handle.

Frequently asked questions

FAQ
How does the 999 THB starting price work, and why isn't there a fixed price?
Because "a plugin" can mean wildly different jobs — anything from adding a single button to building a whole booking system. So we scope the requirement first and then quote the real work. Work with a clear scope that fits in one file starts at 999 THB; anything with admin screens, a database, or several API integrations costs more than that. Either way, you get the price before we start.
Will it work with the theme or page builder I'm already using?
Yes. We build on standard WordPress hooks and filters, so the plugin works alongside Gutenberg, Elementor, Bricks, Kadence, Divi, Astra, GeneratePress or a custom-coded theme. If you want, we can also expose it as a block or an element inside the page builder you use.
Why build a plugin? Can't it just go in functions.php?
It can, but we don't recommend it. Code in functions.php disappears when you change theme, and often disappears on a theme update if you're not using a child theme. Keeping it in a plugin makes the functionality yours rather than the theme's: you can switch it on or off, move it to another site, and track down problems far more easily.
What do I receive at the end, and who owns the code?
You receive all the plugin files with full rights to use them on your site. No licence lock-in, no compulsory monthly fee, plus a short manual covering where the settings are and how it works. If you later want another team to maintain it, just give them the files.
Is there a warranty or bug fixing?
Yes. We fix bugs within the agreed scope free of charge for 30 days after handover. New functionality added later is quoted as additional work. After the 30 days you can choose ad-hoc support or a monthly arrangement.
How long does it take?
Small functions with a clear scope are usually done within 1 to 3 working days. Work involving admin screens or external integrations usually takes 1 to 3 weeks, depending on how ready the other system is and how many rounds of testing are needed. We put the timeframe in the spec before we start.
What if this plugin breaks my site?
We back up the site before every installation and test on a staging site before going live. If something goes wrong after installation, deactivating the plugin returns the site to exactly how it was — because we never edit theme files or WordPress core files.
Will you fix a plugin someone else wrote?
Yes, as long as the code is readable and not encoded. We assess first whether it's worth continuing with it or better to rewrite. Sometimes rewriting is cheaper than chasing bugs through the old code, and we'll explain our reasoning before you decide.

Tell us the brief first, then decide

Scoping the requirement and quoting it is free. If an off-the-shelf plugin already covers what you need, we'll tell you straight.

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