Custom ERP Development in Thailand

What an ERP actually solves

Follow one order through a company without a central system. Sales types a quotation in Word, the customer confirms on LINE, the warehouse checks stock in one spreadsheet, accounting re-keys everything into the accounting program to issue a tax invoice, and at month-end a manager collects files from everyone to build a report. The same data is typed three or four times, and every time is a chance to get it wrong.

An ERP (Enterprise Resource Planning) system puts sales, purchasing, inventory, production and accounting on a single database. A quotation becomes a sales order, the sales order reduces stock, the delivery triggers a tax invoice, and the payment clears the receivable. Management sees live numbers without waiting for anyone to merge files.

Southern Whale’s custom ERP development starts with how your company works, not with a product to sell. We map who handles each document and who approves what, then build the system to fit, either by customizing an open-source ERP such as Odoo or by building from scratch, whichever makes more sense for your situation.

Honest note: not every company needs a custom ERP. If your processes are standard and a monthly SaaS product covers them, that is usually cheaper and faster. We’ll tell you so in the first conversation.

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The accounting back office comes first

For most Thai businesses the daily pain is not manufacturing or warehousing; it’s the paperwork on the accounting side. So we treat the accounting back office as the core of the ERP.

Order to cash: quotation → sales order → delivery note / invoice → tax invoice → receipt → receivable cleared. Each document pulls from the previous one, VAT at 7% is calculated automatically, and document numbers run in the sequence your accountant requires.

Procure to pay: purchase request → approval → purchase order → goods receipt → supplier invoice → payment → payable cleared. When paying service providers, withholding tax is calculated by income type and the withholding tax certificate is generated from the same record.

AR and AP: aging reports by overdue bucket, upcoming supplier payments and balances per customer or supplier, so finance knows who to chase and who to pay today.

Tax and accountant handoff: input and output VAT reports, withholding tax listings for filing, and exports of journal data your accountant’s software can import. Your accounting firm starts from clean, complete data instead of a box of paper.

The system does not replace your accountant. Closing the books, filing taxes and accounting judgments remain with your bookkeeper and auditor.

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Who it’s for

• Distributors and wholesalers with hundreds or thousands of SKUs, customer-specific pricing and credit limits
• Small and mid-sized factories that want sales linked to materials and production (see MRP system)
• Resorts, hotels, clinics and tour companies in Southern Thailand that already have a booking or front-desk system but still consolidate accounts by hand
• Multi-branch or multi-entity companies that need separate tax documents per entity and one consolidated view
• Organisations with multi-level approvals and a need for a full audit trail

A typical scenario: a building-materials distributor whose salespeople give discounts freely, and accounting only discovers the lost margin later. Approval rules and a single source of data fix that.

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Signs you need an ERP

1. The same data is entered more than once
2. Stock in the spreadsheet doesn’t match the shelf
3. Month-end close takes several days
4. You can’t see who owes what and for how long
5. Critical spreadsheets depend on one employee
6. Management decisions wait on late or incomplete numbers
7. You bought software nobody uses because it doesn’t fit the workflow

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Modules we build

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Off-the-shelf, Odoo, or custom build

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Our process

1. Discovery — interviews with sales, warehouse, accounting and management; sample documents and spreadsheets; a written scope.
2. Prototype — clickable screens your team tests before we build, so field names, steps and document layouts match what they know.
3. Phased rollout — start with the highest-pain module, run it alongside the old method briefly, reconcile, then move on.
4. Training — by role, with a Thai or English manual containing screenshots.
5. Handover — source code, documentation, database diagram, top-level admin account in your company’s name, and server access.

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Integrations

• Your accountant’s software (Express, FlowAccount, PEAK and others) via import files or API where supported
• e-Tax Invoice & e-Receipt via an approved service provider
• Your website or online store, so web orders and stock stay in sync
• LINE Official Account notifications for approvals and customer documents
• Existing booking or front-desk systems
• Excel and Google Sheets import/export on every table

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Data migration, security and PDPA

We build import templates, clean duplicates, load opening balances for stock, AR and AP at a cut-off date, and reconcile totals against your source files for sign-off. Not all history needs to move; we help you decide.

On security: role-based access (sales staff don’t see cost prices), audit logs, issued documents that can only be voided and reissued rather than overwritten, automated and tested backups, HTTPS, optional two-factor authentication for admins, and personal data kept to what is necessary under PDPA.

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Why Southern Whale

We have delivered more than 50 websites and systems for businesses, and our founder has over 10 years of web and systems experience. We aim for systems your team can keep using after handover without calling us for every change.

ERP is part of our custom software development service. Related services: CRM, MRP, inventory and POS.

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Let’s talk about your ERP

Send us sample documents or describe the step that wastes the most time. We’ll tell you where to start, whether off-the-shelf would do, or whether a custom build makes sense. Priced on real scope — message us on LINE for a free consultation first.

Frequently asked questions

What is an ERP and how is it different from accounting software?

An ERP puts your core operations (sales, purchasing, inventory, production and accounting) on one database, so data entered once flows to every department. Accounting software focuses on bookkeeping and tax. Many Thai companies use both: the ERP runs operations and feeds clean data to the accounting program their accountant already uses.

Do we have to stop using Express, FlowAccount or PEAK?

No. If your accountant is happy with their current program, we design the ERP to export data in a format that program can import, or connect through its API where one is available. The right method depends on the program and version; we check this during discovery.

Can the system issue Thai tax invoices, receipts and withholding tax certificates?

Yes. Documents are generated directly from sales and purchase data, in the layout your company already uses. For e-Tax Invoice we integrate through a Revenue Department-approved service provider, and we ask your accountant to review document formats before go-live.

Do you build on Odoo or from scratch?

It depends on your process. If it is close to standard ERP flows, extending Odoo is usually faster. If your process is very specific, or you want a lean system tailored to a small team, a custom build can be the better investment. We explain the trade-offs before you commit.

Can you migrate our data from Excel or an old program?

Yes. We prepare import templates for customers, suppliers, products, opening stock and outstanding AR/AP, de-duplicate records, and reconcile totals against your source files so your team can sign off before go-live.

How long does an ERP project take?

It depends on the number of modules and how complex your workflows are. We recommend phased rollout, starting with the most painful area, such as order-to-cash. You get a timeline after discovery.

Where is our data stored, and is it secure?

On a server or cloud account your company owns. We use role-based permissions, audit logs, automated backups and a design aligned with Thailand's PDPA for customer and employee data.

Do we get the source code?

Yes. We hand over source code, system documentation and server access so any competent team can maintain it. You are not locked in to us.

How much does a custom ERP cost?

Priced on real scope: number of modules, users, integrations and data to migrate. Message us on LINE for a free consultation first, and we'll send a written scope before any work starts.