Custom Software vs SaaS: Decision Framework for Thai SMEs (2026)
Every Thai SME that grows past a certain point hits the same question: “Do we keep using SaaS, or invest in a custom system?” The honest answer: “It depends on the 5-year TCO — not the monthly price.”
This article breaks down the math line by line, with the decision framework we actually use with clients.
What SaaS Is and Why It Works
SaaS (Software as a Service) is software rented monthly — HubSpot, Slack, Notion, Zoho CRM, Shopify.
Strengths:
- Fast to start — sign up + setup in 1-2 weeks.
- Low upfront cost — starts at 500-5,000 THB/month.
- Has support, ships new features regularly.
- No internal tech team required.
Best for:
- Startup phase when workflows aren’t stable yet.
- Standard functions every business needs the same way (email, chat, docs).
- Small user count, under 20 people.
What Custom Software Is and Why It Works
Custom Software is a system built around your specific workflow. The codebase is yours, hosted on your cloud.
Strengths:
- Workflow matches the business 100% — no forcing the business to bend to the SaaS.
- Long-term TCO lower than SaaS (past the breakeven point).
- No vendor lock-in — no fear of the SaaS tripling its price next year.
- Integrates with your legacy systems.
- Data sits on your server — better privacy and compliance.
Best for:
- Businesses with unique workflows SaaS doesn’t address.
- 50+ users on the same system.
- Need for legacy integrations.
- Regulated industries (Healthcare, Finance).
5-Year TCO — Real Numbers
Real example: a tour booking system for a business with 15 users.
Option A: SaaS Stack
| Tool | Monthly × 5 years (THB) |
|---|---|
| Bookeo Booking System | 8,000 × 60 = 480,000 |
| HubSpot Starter CRM | 4,500 × 60 = 270,000 |
| Mailchimp Standard | 3,000 × 60 = 180,000 |
| Slack Standard (15 users) | 4,500 × 60 = 270,000 |
| Google Workspace (15 users) | 5,400 × 60 = 324,000 |
| Notion Team | 2,250 × 60 = 135,000 |
| Integration Cost (Zapier Pro) | 3,500 × 60 = 210,000 |
| 5-year TCO | 1,869,000 |
Option B: Custom System + Lightweight SaaS
| Item | One-time / Monthly (THB) |
|---|---|
| Custom Booking + CRM Build | One-time 800,000 |
| Hosting (Vercel + Supabase Pro) | 1,200 × 60 = 72,000 |
| Maintenance Retainer | 15,000 × 60 = 900,000 |
| Email (Google Workspace, 15 users) | 5,400 × 60 = 324,000 |
| Mailchimp Standard | 3,000 × 60 = 180,000 |
| 5-year TCO | 2,276,000 |
Option C: Full Custom (No-SaaS)
| Item | One-time / Monthly (THB) |
|---|---|
| Custom Build (Booking + CRM + Email + Internal Chat) | One-time 1,800,000 |
| Hosting (Self-managed) | 3,000 × 60 = 180,000 |
| Maintenance + Feature Development | 25,000 × 60 = 1,500,000 |
| 5-year TCO | 3,480,000 |
Breakeven analysis:
- Years 1-2: SaaS is cheaper.
- Year 3: Options A and B converge.
- Years 4-5: Option B comes out 10-15% cheaper than A.
Conclusion: for medium-sized systems used 5+ years, Option B (Hybrid Custom + Lightweight SaaS) wins on long-term cost and delivers a workflow that matches the business.
Hidden Costs SaaS Doesn’t Advertise
- User-based pricing scales — 15 users this year, 50 next year, cost triples.
- Add-on tiers — need feature X? Upgrade to Enterprise tier (2-5x the price).
- API rate limits — exceed quota, pay for add-ons.
- Integration cost — Zapier Pro at 1,500-5,000 THB/month if your workflow is complex.
- Vendor lock-in — switching costs 200,000-1,000,000 THB in migration.
- Data export limits — many SaaS providers restrict how you pull data out.
Decision Framework — When to Switch
Score yourself on these 7:
- Your workflow is unique and no single SaaS covers it end-to-end → Custom
- 50+ users on the same system → Custom (per-user pricing compounds)
- Combined monthly SaaS cost over 50,000 THB → Run a TCO breakeven calc
- Need to integrate legacy systems that have no API → Custom
- Data privacy / compliance is critical (PDPA, ISO 27001, Healthcare) → Custom
- Workflow shifts constantly with seasonality/business → Custom
- Want to own the asset long-term → Custom
If you say yes to 4 or more, a custom build is starting to pay off.
How to Start Custom Software Without Burning Cash
- Start with an MVP — not a big-bang build of the entire system at once.
- Phase-based development — ship every 2-week sprint.
- Pick a tech stack you can maintain long-term — Next.js + TypeScript + Supabase/Postgres is our default.
- Documentation + tests from Day 1 — so your internal team can pick it up later.
- Use AI-augmented development — cuts time-to-market by 40-60% (Vibe Coding).
Ready to Calculate Your Own TCO
Let’s talk — the first discovery workshop is free, we’ll work out your 5-year TCO line by line, and we’ll give you a straight answer (including “stay on SaaS” if that’s the right call).
See more: Custom Software Development Service